Here's a little more info that might be helpful.
First Acrylic or water based paints...createx and parma faskolor, want to adhere to it's self not necessarily plastic. If you spray your first layer to THICK, the paint will form a "skin" of dry paint on the outer side of paint. As the inner paint dries it will adhere to it's self and much less likely to adhere to the plastic. If you apply a THIN coat first, just a "dusting", it will dry and attach to the plastic because it isn't thick enough to create an outer skin. the second coating of paint will adhere to the first layer as it wants to adhere to it's self. You eliminate any possible problem by apply a thin coat and wait a minute for it to dry.
Second, Lacquers, Enamels etc. These paints can have a chemical reaction to the plastic during the drying, bonding process. No need to scuff the body as these paints tend to "burn into" the plastic. these paints can dry or "flash" much faster than acrylics so you have to be careful not to hold the air brush or spray can to far away from the plastic. These paints can literally flash in the air, hitting the plastic dry, which would cause chipping etc. This happens usually when your painting out side in the heat of summer.
The only problem with scuffing a body is if you are painting with any transparent or translucent color and back it with white or mirror chrome, you'll probably see the scuff marks
hope this helps
caci623