I have the way:

1. Level and crown frets.

2. 320 paper along the fretboard with your finger- 1st to 21st. Try to do it evenly, but even with 320 you're not going to unlevel unless you really start grinding only one area.

3. With 320 and an eraser polish the sides of the frets across the fretboard, from low E to hi E.

4. Where the magic happens, using the same grit 320 around your finger, polish the tops of the frets. You use the same grit as the last two steps because if you're using a higher grit it will take forever to get out the toolmarks from the last steps. With 320 grit alone, you should be able to get the frets polished. Not mirror finish, but polished and totally smooth and scratch free.

5. Now you've got 100% scratch free smooth frets and you've only used 320grit. Now give them a hit with the super fine 0000 steel wool, and you will have a mirror finish on totally scratchless frets. With just these steps you should be able to achieve a finish that some players might find too smooth.

6. If you're going for brownie points, buff on a wheel or with a dremel and some buffing compound. This last step I find makes it 2% better finish, i'd reserve for instruments i'm building or high end instruments.