I do quite a bit of work with Tru-stone and my finishing process is to sand with the following grits: 150, 220, 400, 600, then micromesh through 12,000 (very lightly). At this point, the piece will look shiny, but if help under a light will still show light scratches. I finish on the 3 wheel buffer using all three wheels (Tripoli, White Diamond, Finishing wheel) holding the piece lightly against the wheel. As a note, I have turned Delrin bushings that I use for the buffing process to keep the wheels as clean as possible.
I recognize that my finishing process may be viewed as overkill, but it achieves the results I'm after.
Below is a custom shaving brush with a Wild Horse Jasper handle. The picture is a little dark, but the finish is without a blemish and shiny.
Bob