Tried it, but was not a fan. We found systems that worked better for us.
I have heard others who've done it successfully and would do so again.

How old is the child? 

I used this book when I had babies.  It worked well for us.

https://www.google.com/aclk?sa=l&ai=DChcSEwjDxPCKxpWHAxX-T0cBHdiNAtgYABAEGgJxdQ&gclid=Cj0KCQjw-ai0BhDPARIsAB6hmP7zZ9AyH00waN2mV32CRyMaNdIKoJrQOeAsrGtwIuwj2MqkIseCt3kaAnTCEALw_wcB&sph&sig=AOD64_3-2lQyaQiRqnkvtsggR0EWnRCyRQ&rct=j&q&adurl&ved=2ahUKEwjImeqKxpWHAxWDEVkFHU8ICP0Q0Qx6BAgREAE

11 months. 

I liked that book, but that system didn't really work for me either. The Eat-Activity-Sleep-You system was always E-A-E-S-Y for my babies. That was alright for me, but it didn't result in anything astonishing like sleeping through the night.

Hey that was the same for me.  It helped my first sleep through the night, but as I had more children it started working less.  I guess I meant by it worked well was that it relieved some of my stress.  It wasn't perfect.

Disputationes, I see your a man, are you asking for a wife or a family member?  Sleeping issues are hard and stressful.  Do you know other Catholic families who have children?  It is hard to help via online because there are so many variables involved.

I am of the opinion that sleep training (cry-it-out) could be used if the mom or anyone is so sleep-deprived that it's affecting their ability to function. But generally, babies have "sleep regressions" so I don't know if training a baby to sleep through the night is going to work unless you rely on cry-it-out. We don't have soundproof walls at the moment so when we did try it, it was resulting in less sleep. It's also quite painful hearing your baby screaming to the point when you think they're going to vomit. What did work for us, was cosleeping. Back then, houses were much smaller so you couldn't just put the baby in its own nursery room, shut the door, and walk away. In our current living situation (our house is currently being renovated) the baby had to sleep in the crib with us so a separate room for her was not possible. 

Our baby has never taken a pacifier and even if she had one, she wouldn't like it. For every nap and night sleep, I nurse her to sleep. Whenever she cries in the middle of the night, I'll let her fuss and sometimes she'll go back to sleep but most of the time I nurse her to sleep and it only takes a few minutes. We all get better sleep. I recommend getting a co-sleeper bassinet, put the baby in the bed with you (with rails or put the bed against the wall), or do a side-crib (put the crib up against the bed with the railing removed). 

Recently, a few months ago, she has gotten bigger and doesn't fit in our queen bed. She sleeps in between my husband and I. I used to think that people who coslept with their babies were weird and kind of reckless, but I was at the point of sleep deprivation that I had to do something. It turned out that she just wanted to near us and that warmth of my arm around her head gave her the ability to fall back asleep without even having to nurse because she knew she was safe. But, when your almost 14-month-old is kicking and thrashing in the middle of the night and every creek in the bed wakes her up, I knew I had to do something.

A week or two ago, I decided to put her in the playpen and lay down with her (on a twin mattress) and nurse her to sleep or just be near her until she falls asleep. And, then I could go to sleep in our master bedroom. She still cries but she sleeps much better and has more space. I don't want to night wean her yet but it'll be a gradual process. I do miss my sleep and it's been more than a year of bad sleep. It's funny but I see these toddlers with pacifiers in their mouths and society can't connect breastfeeding with that, like it's a stigma. Like what did people do before pacifiers were invented? Probably coslept on a floor bed until the next baby came, I donno. 

I'm also a first-time mom and I heard that all babies are different, only speaking from personal experience. I don't expect my future babies to be the same and might have to innovate ways for different sleeping arrangements. 

We do a mixed version of sleep training.  Really it doesn't matter what method you use as long as your find something that works for you and your child.  Every child is different but this is our general method:

Our babies usually co-sleep for the first 2-3 months when they want constant reminders of your presence and constant nursing.

Once they start rolling around 3-4 months then they graduate to a bassinet in our room for safety sake (they also tend to sleep a little better with a little distance at this point).

Around 6 months I find that baby and I tend to wake each other up a lot if we are in the same room.  So, I then move baby to the nursery (which we also use as a guest room and if we have guests we just put baby temporarily back in our room).  The babues would usually still nurses to sleep at this point.

Around 9-12 months we start "sleep training".  Basically,  I will give them a chance to fall asleep nursing, but if they don't fall asleep I will lay them in their crib and walk away for 15 minutes.  If they are still crying after that time I get them and try again when they seem more tired/hungry.  Gradually they get used to the system and start accepting it and falling asleep by themselves without crying though they are still awake when I put them down in their crib.

Once they are "sleep-trained" there will still be night where they have nightmares or are sick and need extra help getting back to sleep.

It is definitely exhausting.  But keep trying and eventually something will work out.  :)

Currently our youngest is 17 months and he usually sleeps through the night (unless sick or disturbed) and goes to sleep without crying. 

We have a simple "bedtime" routine so that all our 3 little boys know it is time for bed.  Everyone gets changed, brushes their teeth, we pray night prayers, everyone gets tucked into bed and usually we don't hear more than a peep from them until the morning (baby included).

Ditto.  This sounds like how it worked for me.  Thanks for the reminder.  My youngest out of 5 is now 8.

We do a mixed version of sleep training.  Really it doesn't matter what method you use as long as your find something that works for you and your child.  Every child is different but this is our general method:

Our babies usually co-sleep for the first 2-3 months when they want constant reminders of your presence and constant nursing.

Once they start rolling around 3-4 months then they graduate to a bassinet in our room for safety sake (they also tend to sleep a little better with a little distance at this point).

Around 6 months I find that baby and I tend to wake each other up a lot if we are in the same room.  So, I then move baby to the nursery (which we also use as a guest room and if we have guests we just put baby temporarily back in our room).  The babues would usually still nurses to sleep at this point.

Around 9-12 months we start "sleep training".  Basically,  I will give them a chance to fall asleep nursing, but if they don't fall asleep I will lay them in their crib and walk away for 15 minutes.  If they are still crying after that time I get them and try again when they seem more tired/hungry.  Gradually they get used to the system and start accepting it and falling asleep by themselves without crying though they are still awake when I put them down in their crib.

Once they are "sleep-trained" there will still be night where they have nightmares or are sick and need extra help getting back to sleep.

It is definitely exhausting.  But keep trying and eventually something will work out.  :)

Currently our youngest is 17 months and he usually sleeps through the night (unless sick or disturbed) and goes to sleep without crying. 

We have a simple "bedtime" routine so that all our 3 little boys know it is time for bed.  Everyone gets changed, brushes their teeth, we pray night prayers, everyone gets tucked into bed and usually we don't hear more than a peep from them until the morning (baby included).

Since we ditched the scheduled naps around the day, she’s been sleeping a lot better and for longer, last night she slept 8 hours straight and 10 something total. She only woke up once for a quick nursing around 9 or 12 something (don’t remember) and then we put her back in the crib. 

What experience of parenting did St John Vianney and St Alphonsus have?

What a disrespectful thing to saint of these 2 great saints!