Just use 0000 steel wool.
No need to mask the fretboard.
Take a piece of heavy duty paper, and with a utility knife/exacto, cut a slot in the paper just a little longer than your frets.
Place the paper over each fret and polish side to side. After you do every fret, go up and down the neck, masking your neck pickup.
No need to cover the fingerboard when going with the grain of the neck. Then simply condition the neck, wipe it down with a t shirt...done
About 10 minutes and you have new frets...