To polish most types of acrylic, including glitter, fine grit sandpapers are the best option alternating between wet and dry. Using a piece of wet, 800 grit sandpaper in a circular, buffing motion and then repeat with a dry piece of the same sandpaper. Alternating between the wet and dry pieces for a few minutes at a time. Move onto the grade 1200 paper and continue with the circular buffing motions, if it begins to look frosty this is just part of the process and these will disappear during the sanding. Next, dry the area fully with a soft, dry cotton cloth. If you have acrylic polish, this will help the material shine and look as good as new.