kind of late reply, but in case you still wondered.
You put it on and don't take it off when they pout or pick at it. Reward them w treats and whatever kind of other rewards they get right after you put it on. (and even while you're putting it on if you can get a helper. It gets easier when you find a method you can stick with constantly. You have to be consistent. Fo instance, Dandy gets her diaper within minutes of getting out of her kennel every morning, and comes out when she goes to bed (which is when I feed her at night) She knows it's going to happen. She still picks at it when I first put it on but she gets over it after she sees that pouting and picking aren't getting her anywhere. She loves my necklaces, so I let her play with them while I put the strap part on, and her head in my armpit area for the diaper part, then she gets cheese shreds (SHE LOVES CHEESE) as soon as we are finished and before she has a chance to pick at it. That way I'm rewarding her stillness and cooperation not her picking at it. When I see her picking at it, I tell her to stop it ( one of the 2 verbal commands she knows) and distract her with a toy.
The surgical masks actually work great with chickens, and you don't wash them. Just make sure you get the ones that don't have the wire strip for the nose part, or that you pull it out before putting it on your feathered lovey.
I would put something on them even growing. Even if it's just a sock that's cut or something to get them used to the presence. You can fine tune and go for productive outcome once they are grown, but the longer you wait to start it the longer they take to get used to the idea.
