There are many ways to improve the surface finish of casting. One common approach is to use a sanding disk. This disk has hundreds, sometimes thousands, of tiny holes that allow it to easily achieve a smooth finish. Another way to improve the surface finish is to use a polishing compound. This compound removes the scratches and blemishes from the metal, resulting in a smoother finish. Both of these methods require some experience and some experimentation to find the right combination that produces the best results. However, by using these techniques, you can significantly improve the overall appearance of your casts.