For a flat black a lot of people are using John Deeres Blitz Black paint that is cheap as hell. Only like 22 bucks for a gallong and then they say to use their primer which is I think only 12 bucks and then their thinner and a hardener. I have seen some done with this black and it's awsome. It's a flat black as well with a tad bit of a shine but you can't tell unless it's next to another flat black vehicle. I would say to air brush over the flat black with a gloss color but not sure. Spraytech and DangerousToy are the paint pro's here.