I love highly polished frets. My polishing routine is the following:
After masking the board, I start with the
3M micro mesh sanding papers working though the progression of 1,500, 1,800, 2,400, 3,200, 3,600, 4,000, 6,000, 8,000, and 12,000 grit. That basically yields a mirrored finish as it is, but I follow that up with black, green, and white
polishing compounds on a
rotary tool at about 5,000 RPM using the
Dremel 429 1 inch felt polishing wheel (single grit per wheel to avoid cross contamination). That sequence will give you totally mirrored frets. I have never had an issue with excess heat buildup when using the rotary tool.
Stainless steel frets basically only need to be polished once and then they will stay glassy smooth for years. Nickel frets tarnish slowly and will benefit from polishing with the rotary tool (or the 12,000 grit micro mesh if I'm being lazy) about twice a year.