Brownell's www.brownells.com has -- or at least had, several years ago -- a couple of ways of doing this. Besides the ones already mentioned, they also sold small steel bristle brushes on an arbor, with a small O-ring to put around the bristles to stiffen them. The idea was to apply some lapping compound of suitable grit, and bring the rotating brush down on the workpiece.
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Everybody is ignorant, only on different subjects. -- Will Rogers
There are lots of people who mistake their imagination for their memory. - Josh Billings
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