I think it was just masked off. My door handles were painted at the same time. I'm going to paint my new Engelmann mirrors when they arrive although not sure if I might do them body colour as opposed to all black?
Use plasti-dip! Its a thin layer of rubber that sprays from a can. Since it's not paint, it hold up to abuse way better! And you don't have to worry about priming or anything, because plasti-dip will stick to anything.