Build it up in many layers and turn your pressure up so the paint is dry as it hits the surface. I always airbrush Tamiya flat black on the back of windows and turn the pressure up to about 25-30 psi and put it on lightly. You will have better results with a good dual action air brush because they mix the paint internally and atomize the paint better. I use the Badger Crescendo 175. If the paint is going on too wet it will not stick good.