To do a perfect job, you need a lapping machine. Not really an option for the diy'er!
Short of this, it is possible to achieve a reasonable finish with abrasive sticks. A basic jig will help you keep the grain straight and concentric. There is an excellent thread on thewatchsite describing one approach to this. I have included a link below.
I would practice on a scrap case first, be very careful when you reach the edges of the case to avoid rounding them
http://www.thewatchsite.com/21-japan...added-how.html