“Cultured marble” is actually polyester resin, which means that you can buff out light scratches using the same supplies and techniques a Corvette owner would use. At an auto parts dealer, buy a buffing pad that fits an electric drill, medium-cut rubbing compound, and paste wax made for fiberglass cars. Buff the surface with the compound and buffing pad, then rinse, apply the wax, and buff until shiny.