Purgatory by Fr. Schouppe makes no mention to this.  You did not say what church you are attending, that is traditional or such.  Those in purgatory need prayers approved by Holy Mother Church that have indulgences and such.  Of all the stories I have read of those souls begging to get out of purgatory, they beg for the Precious Blood, the true Mass.

It was an SSPX priest. Thanks.

You didn't think to ask the priest. I've never heard of such a practice.

Genuflection is for Our Lord, Our Lady, but my soul tells me, stick to what works and is approved by the Christ and what the souls need most, to be remembered at Mass/Eucharist and prayers.

 The original post was mine. I will ask the priest, who is European, at the next opportunity. My family is new to Tradition, and had never heard this before. I thought it was a bit strange that no one else in the chapel stayed behind after Mass to try to fulfill this, only my family members and I. (Let me tell you, it is a bit of a work out!) But it sounded like a wonderful indulgence on behalf of the Poor Souls, so we attempted to do as the priest suggested.  (However, I didn't see him doing it) But I tried googling it and couldn't find anything about it even being a European custom. So I thought I would ask here. Thanks.