Concerning the ordinations, I can say that in the early days, there were a few that were ordained in the old rite by true bishops. One that is docuмented is Fr Frank Quoex, ordained in 1992 of ICKSP by "Cardinal" Pietro Pallazzini, who was consecrated in 1962
http://www.newliturgicalmovement.org/2010/01/life-work-and-ambitions-of-abbe-franck.html#.X9BZedhKiM8 Also, currently stationed in Sulphur, Louisiana is Rev Canon Jean-Marie Moreau who was ordained by Bp Pallazzini as well on Oct 7, 1992.
https://tlmofsf.com/2015/10/07/happy-23rd-ordination-anniversary-canon-moreau-ad-multos-annos/ Besides the few from the SSPX, a few, old-rite ordained priests joined up. In the Fraternity, Fr James Buckley, ordained in 1965, serves as spiritual director at their American seminary. He is a good Ignatian retreat director. Fr Irwin, who is recently deceased, was old rite. There may have had a few more, but time has marched on. I know that in the Coeur d'Alene area, an elderly priest says Mass on occasion at their chapel, having had maintained his own chapel before in Oklahoma.
I can recall reading in "The Latin Mass Magazine", from when they started, through the 90's, that they would make mention of ordinations of these groups, and who was ordaining them. It may be one of the best sources, if you can find copies of them, of what priest was ordained by what bishop, and when, telling you who is a priest, and who is not, or is at least doubtful. Hard to find on the net much about the ordinations that happened before the 2000's,. Perhaps "Christian Order" from their early days would be another source. One can always ask, but some get touchy about that.
As alluded to by someone above, it is can be more dangerous than Russian roulette.
Just thought I would offer this.