I've used Autosol polishing compound for many years on frets, but I recently decided to try this one from Menzerna - I'm glad I did!
You can buff it by hand, with a soft microfiber cloth or use it on a Dremel tool, like I do, with a soft polishing wheel. I run my Dremel on the lowest setting, which is recommended when polishing. I polish my frets with 320 grit sandpaper and then a sanding stick, also with 320. I'll go up and down the neck with the sandpaper and then go across with the sanding stick, to switch directions and take out even further scratches.
From there I do 400, 600, 800, 1000 and 1200 grit.
Lastly I use 1500 and 1800 grit Micro Mesh belts, on the sanding stick as well. Then it's time for the Menzerna polishing compound. This leaves a mirror-shine.
Highly recommended!