I was working on a M1A2 Abrams one late night when it came time to put on the non-skid surface on the tank. I started walking around the kitchen to find something to us. Long story short, baking soda! this is how it works. Get out your model masters flat clear finish" this is what i used". i'm sure your could use somthing close to it. Paint it on " thin coats" with a brush in small sections at a time, then sprinkle on the baking soda. Then air brush your base coat let dry and wash & weather. And it wont rub off either. I had good results and the scale is'nt bad either. Try it on scrap plastic first.

I've tried a few methods and the quickest and IMO best results have come from using textured paint. Rust-Oleum makes a bunch of them in many different colors and textures.