Hello, I bought some Testors MM Acryl silver and Tamiya Acryl silver to paint CW Vortex's missles silver, but the paint won't stick. When I put it on, it just runs right off and you can see the original color underneath. I tried some enamel paint and it stuck, but it chips very easily. Do I need some acrylic paint primer? And if so, will any generic kind do, or are Testors/Tamiya primer better? Sorry, I don't know much about paints and I'm just a beginner. Thanks!