The process is to do grinding first. Polishing second, and buffing third. In general, grinding permits far more aggressive a Rading action than polishing. Likewise, polishing is a far more aggressive abrading action than buffing.
In grinding, polishing and buffing, labor is a major variable in the process. The requirement is for highly skilled labor with a years of experience and a thorough knowledge of the art of their craft. Special mechanical polishing procedures required for preparing metal surfaces, such as stainless steel for electro polishing.