W Metals can be directly painted on plastic, without primer. Here how to use them by airbrush :
Both for airbrush or brush, you can use them without without thinning, or thinning with simple water.
If you need or if you like to use of a primer, it's advisable to use True Earth's SLICK PRIMER or WHITE PRIMER.
Both for panel lines and for more or less marked effects of wear, you can combine the basic painting with W Metals together with METALINER products.