i did that a couple of times, when i still cared very resistant and virtually indistinguishable (this of course would depend on the original finish, location, size and shape of the nick, etc. i'm talking tiny tiny ones)
unless your original finish is very shiny, you should be ok with the "flat black", don't be tempted by the polished-mirror "glossy" ones. try on a small nick, wait a day; if you don't like it, rubbing alcohol should take care of it
ps. hands off them brassing, we loves brassing!