This happens frequently unfortunately, especially rescue chooks. Anyway, have done just as you have quite a few times, sometimes it works, sometimes not, but its worth a go. Re pooping - Last success I had Prep H, had to keep pushing it back in few times every day for ages. Then tried "people"...
Had similar problem with 1 of my rescues. Did what you did, Prep H and replaced - then (in desperation) tried a human pantie liner taped each end to chicken (extra sticky tape!) which left a small gap for any poop - which was left on the pad sometimes anyway. This took a LONG time putting back...