Rub it back with about 400 grit wet & dry, prime it with about 4 - 5 coats & let that dry for a day, rub that back with 4-600 wet & dry then paint it with at least 6 coats of black & a few of clear ( if you want )then leave it for about a week to dry properly then rub it back with 1500 wet & dry then use a good buffing compound then polish it, but that's if you are using acrylic which is the cheapest option.