A lot of the things I suggest might run contrary to 'good bird care' or the 'way things are supposed to be', but I'm not one to fight the flow of what the bird wants in favour of what 'is good for it' when it comes to plucking. That said, YMMV with what I suggest.
First step---take that collar OFF! They do more harm than good and the stress they place upon you and the bird's relationship/trust (plus just on the bird in general) is not worth it *unless* you start seeing bloody wounds---bald spots are just bald spots. I'd rather damaged follicles than a damaged relationship or mind.
Second---especially in a bird that young (older birds can sometimes through sexual frustration etc become the often cited 'behavioural' pluckers---but even then) go over *EVERYTHING* with your vet. Any vet who suggests 'oh all greys are nervous and pluck eventually' (like mine did

)---slap them silly or find yourself a new vet. Look at every possible organic cause---get a CBC done, check all organ function, look for PDD and other chronic diseases, heavy metal toxicity, fungus/bacterial infection, allergies/intolerances...everything.
The third biggest thing, has been, for me, to reduce stress and anxiety, promoting a sense of safety/security and fulfillment. In other words, think like a parrot and live like a flock.
For example, my TAG wakes up before dawn and goes to bed when my partner and I do, does this get her the 10-12 hours a night? Nope, not even close--on a good night she might get 8. But for the first time ever, generally speaking, there's no down on the sleep carrier bottom in the morning.
If I try to put her to bed without us 'the flock' or get her up later than 5-6 AM or enclose her (either in her sleep carrier or day cage)---she plucks at night.
The solution for her has been sleeping in the open, perched nearby (she sleeps at the head of my bed) and waking/sleeping when the 'flock' does.
As well, foster a sense of community and security--my TAG and I eat, sleep and bathe together. This natural rhythm of living is instinctively comforting to them, she wakes with us, we have 'snooze and scritch' time in the morning for a little bit, we 'fly' to our foraging site in the kitchen and have a bite to eat, then we 'fly' to the shower to have our morning bath, then we 'fly' back down to her day cage and we hang out (or I head off to class), and then lunch, supper and our evening bath (another huge thing with greys---bathing and humidity! If your little guy doesn't like spray bottles for now just bring him in the shower and let him sit in the steam with you) before we settle down for bedtime. Try to fufill as many natural desires and modes of living (like foraging for all his food and travelling within the confines of your home) as you can.
As well, keep up the toy rotation and enriching environment.
As far as distraction goes try to stop that, as it may be reinforcing it. You don't want him to pluck for attention if he isn't already. The biggest thing however is acceptance and keeping your own feelings in check, if you're stressed and anxious it will make the plucking worse. He may pluck forever, but learn to love and accept him as he is.