I need help with Polly Scale acrylics. This is the first time I've tried airbrushing Pollys, but I'm trying to paint US Interior green on an A.M. Dauntless and P-51, and the paint is coming out too thin, then cracking on the plastic. I've stripped the paint, cleaned the plastic, put down a primer coat and started again only to get the same result. Do I need to thin it differently than other acrylics? I usually use a 50/30-40 paint/thinner on Tamiya acrylics and have done the same here.