Homemade handle with radius and self-stick wet&dry abrasive pads for polishing. These also work on the Dual-grit diamond fret files. Maybe the best way to re-crown frets. The 300-grit seems a bit much so I also use end of the diamond file for some paper tab polishing after the 150 grit has shaped the crown.

Custom fret tool for lapping frets.

The old custom fret polisher with self-stick abrasive has worked well. The StewMac Duel-Grit diamond file on the 300 grit side (which I never use for crowning anyway), has a nice radius which also works well with the homemade/double-back tape tabs for polishing.