To polish metallic acrylic, fine grit sandpapers are the best option. Using a piece of wet 800 grit sandpaper in a circular, buffing motion and then repeat with a dry piece of the same grit sandpaper. Keep alternating between the wet and dry pieces, rubbing for two to three minutes at a time. It may begin to look frosty, but this is just part of the process and these will disappear during the sanding. Move on the grade 1200 paper and continue with the circular buffing motions, before drying to area fully with a clean, soft, dry cotton cloth.