no problem painting over a gelcoat.
word of warning though - assemble the car first - then disassemble to paint.
I have had to drill / "fine-tune" my CMc body quite a bit to get it perfect. I've had 14 cars and my advice would be tp paint it *last*, once you have everything sorted out. It'll take a bit longer to remove everything, but assembly will be a piece of cake.
Or, paint the car firrst and worry about scratched / drilling holes, chipping paint during the assembly / test fit stage.
your car. :-) my $0.02