I went back through the grits again starting at 320 and here is the result
The finished polished board
I am allways suprised by the amount of reflection you get on wood just using sandpaper.
I started off with 80 grit to radius the board to 18" then went through the grits, 120, 240, 320, 400, 600, 800, 1000, 1200 and 1500. After 400 you are more or less starting the polishing process as very little material comes off. I found a big difference between the 400 and the 600. At 400 the fret slots could be filled with sawdust quite easilly but at 600 it would have taken at least twice the time.
The next stage is to apply rustins Danish oil and then put the frets in.