for RC bodies (lexan/polycarbonate) Tamiya has the PS line of spray cans and testors has the pectra line. I'm pretty sure they're both flat/dull finishes as when you paint the inside of a clear body it becomes glossy any ways. That should do the trick for you. The other thing I've recently heard was an alternative to tamiya cans, is dupli color vinyl/fabric paint available it CT etc. It has the extra bonding agent that the RC paint has as well as the flexibility in need as RC bodys flex alot, it might be worth a try, but the selection is much more limited color wise.
I race toy cars, and you though paintball was expensive... Rcjunky's feedback