Water based paints don't really skate well and tend to have a matte finish. Oil based paints skate fine, and look great when they dry, but involve a lot of clean-up with nasty chemicals, and the thinner which is already in them can chemically react with any lacquer still on the board from the factory, which while potentially interesting, visually, has an adverse effect on the board's skateability. Use spray-paint. It finishes well, won't react with the lacquer, is cheap, easy, effective, involves minimal clean-up and drys quickly.