If you are burnishing the surface, use 400 or 600-grit sandpaper. Rub the surface in a circular motion until you arrive at the polished look you like. For larger areas, a power sander may be used.
Wipe the surface with a slightly water-dampened rag to remove any plaster dust.
Once sanded, use the flat side of a clean steel trowel to rub the finish for an added polished appearance.
Continue the process until you have completed burnishing.