If your "bodywork" involves extensive contour changes, you might consider "Supafilla." Mix medium viscosity superglue with with an approximately equal mass of TALCUM powder (NOT CORN STARCH OR BAKING SODA). The resulting substance sands easily to a smooth finish & feathers well, is readily scribed, dries quickly (you don't have to wait for it to "gas out"), and DOES NOT SHRINK (be careful not to apply more than necessary). Auto modelers first concocted it years ago to do custom bodywork. Since it contains no solvents, you don't have to worry about softened or distorted polystyrene underneath it, and unlike straight superglue or superglue+baking soda, it doesn't get harder the longer it cures: you can sand it as easily after 15 days as 15 minutes. Best of all. . . it's cheap!!
Rob