RE: flat black
i've never done it, but i don't see why it wouldnt work....
Get some really fine grade sand paper, like 1500-2000 or more. Just sand down the outside till the shine is gone. Take your time and don't baredown hard, let the paper do the work, that way it'll come out even looking. Then spray any black on the inside and it'll look flat and you won't have to worry about chips