Get a tupperware like an old cool whip bucket or something, cut a hole in the top and fill it a little bit with luke warm water, put the chameleon in that and keep an eye on it through the hole in the top - it should help it peel easier.
That stuff will come off once your cage is misted and he climbs through the trees and such rubbing his back.If not then yeah i used to just gently rub it upwards lightly and most would come off.I didnt fight what seemed hard still but misting him with luke warm water should work.Personaly i wouldnt fight him too much over it because i think they stress a bit easier than say beardeds.Good luck.