Hey bud. Are you talkin about making your car a flat black? kind of like an old hot rod?........There is a few options available.... I have painted a few... When you do paint a flat black, You usually do still put a clear coat on top. If you dont, Your finish will get damaged very easily, and it doesnt last. The clear we put on is pretty much the same as normal clear coat except there is a flatening agent which dulls the finish.. Another option is just to finish your car with a black epoxy primer..I think this is the best method because epoxy is very hard and also prevents rust..That is whats normally used on a classic restoration.(not usually used at production bodyshops). If you want to go the cheap way... Theres always tremclad..lol.. If you prep your car properly...tremclad paint actually works pretty decent. You can go with a matte or flat finish, as long as you can spray it evenly...It will look good.
Hope that helps