This video showing how to sand/polish solid surface countertops, put out by The Fabricator Network, walks the viewer through the process of properly finishing solid surface to a matte finish. According to the video creator, the process specifically follows the fabrication manual procedures laid out by Staron Solid Surface.
It explains the sanding techniques, including the tools, equipment and consumables needed, and offers specific steps.
The video goes on to show how to buff the surface with Scotch-Brite, once again showing the materials needed and the complete process.
You may also be interested in this video about thermoforming solid surface.