Sand it smooth, fill in the scratches with 5 minute epoxy. When the epoxy hardens, you can sand it and shape it smooth, then paint over it. The epoxy can be polished to a shiny finish, it is used in making inlayed jewelry. In college I worked in jewelry manufactory, and find this stuff a miracle for things like scratches and chips. It's cheap, and easy to use. It is messy to prepare though.