Not even close to a perch master here but I have been working with Feed training YP this year and I will say I feel it was successful in many ways. First, my training was following all of Bill's advice on how to feed train. I started with 150 perch in 2 cages and fairly quickly condensed my training to one cage with about 85 fish.
I found after release at 20 days it took about a week for things to pick back up. One thing I noticed was the feed trained perch were escorting other perch of differing sizes to feed, so I have to say I strongly believe they learn (Or "can" learn) from others rather quickly-in my experience-which is not enough experience to say that this is normal or maybe not so normal.
I'm sorry I don't know of any suppliers of feed trained YP, but thought I'd share what I have observed from following Bill's training advice.

www.aquaticspecialties.info
May God be with the Overton's Family.