The majority of the rash is just scratches in the paint, not throught to the underlying plastic. Easy. Sand and paint. However, where the shield flexed some of the paint and primer chipped off, and I don't think it would be easy to get a smooth surface. I figured if I could get down to the smooth, base plastic I'd have a better chance at getting a good finish.
yes, use good primer. I'm not sure if you have spray equipment but duratech is the best.... or, you could fill the area with short stand filled putty.. like evercoat, then prime. put it on in layers using something like creditcard... it's better than bondo as it adds strength..