I had a couple of light parallel scratches on the crystal of my Bulova Precisionist.  As I rubbed the Polywatch in with a cotton cloth, I could tell that the white edges of the scratches were disappearing.  After becoming tired of rubbing manually, my wife and I went in search for the Dremel, but its battery was dead.  Next step, the electric drill.  After a couple of minutes, it became apparent that the Precisionist's crystal was too hard to allow the material around the scratches to merge.  However, they are now almost unnoticeable.  I'm certain that Polywatch would work perfectly on crystals that aren't quite as hard.
Note:  With the electric drill, I used one of the Dremel felt tips and it didn't cause any damage to the crystal.