ok, first of all, apply primer (duh) not just a whole bunch of layers of paint, second, use like rubbing alchohol and a washcloth to make sure like no oils are left on the bars, cuz if there is, itll turn out bad. sand paper yeah, and u can use super fine sand paper to even out the primer after it dries, cuz sometimes itll leave little bumps, and i painted my cranks with normal spray paint adn primer, and it still hasnt come off, at all! but then again, if you ride with your feet close to them, then itll probably wear out, but if you really want to paint them, just space your feet a little farther away from the cranks.