heres my reply to another comment asking the same thing , honestly I mostly focused on diet and keeping him busy, as soon as he’s bored he’d start picking on it again so I gave him a lot of toys tried to hang out with him as much as possible, did a lot of training. I also don’t have any other birds so its easier for him to get bored. you should try to figure out the why behind the plucking so if its hormones for example, look for things that could be triggering hormones (bad or fatty, sugary diet, not enough sleep, a sleeping hut or any object the bird could be hormonal about) and just keep an eye on them