My too"Merlin" was a plucker whe I got him...he was almost completely bald on his chest... he came form an alcoholic home....his food wasn't the best, and he was very skinny.........I fattened him up and have now convinced him that its OK to try new foods... but for the plucking I have found cardboard boxes to be the answer...........I was told by the vet I work for after extensive bloodwork and fecals etc., that i shoud put more wood in his cage(bolt it to the sides, hang it, put chunks that he could pick up on the bottom, etc.) that did not really work.........but one day i left a bnox to close to his cage and walah!!!!!he destroyed it.....so now i always keep his cage with boxes..........he goes in and out of them, chews them to bits, carries them around, i also flatten boxes and stick the in the slots of his cage.............he shreds them...........hias cage may look like a homeless person lives there but without the tower of boxes he plucks again.........right now he has a beautiful fully feathered breast!!!!!!!!!!!

I have seen first hand what  a good diet,proper vet care,proper toys and lots of love can do.  However there are lots of time you just have to accept who they are and just love them anyway.  I have heard the AviCalm works wonders.  Good Luck!!!!!