Frei & Borel sells a crystal polishing compound called “Krystal Kleer”. Here is what they say about about using this product with a buffing wheel and Dremel: “Extreme care must be used and if you have an emotional attachment to the watch, then this is not a product for you. Only use on a bench top buffing wheel and with the crystal still in the case using two hands gently place in front on the outer hairs of the fast spinning buffing wheel for just a few seconds. Too much pressure and you will burn a hole in the crystal this also only takes a second to happen. It is not advised to use a Dremel type hand tool, since all it takes is one slip and the crystal is destroyed.”
I can't imagine they sell much of this stuff, as the sales pitch likely scares off all but the most self-confident watchmakers. I'll stick with wet-sanding (600) ollowed up with toothpaste for final polish.