Sometimes I make little turned vessels with drilled-out interiors, and need to clean up the relatively deep openings. I’ve found that the best tool for the job is a 1/2"-diameter dowel that I use as a drum sander of sorts. I bandsaw a slot in the end of the dowel to accept a strip of sandpaper that automatically wraps itself around the dowel as it spins inside the hole. Refreshing the paper occasionally is a simple matter of tearing off the used section. This technique actually works well for sanding the edges of pierced scrollwork too. On large workpieces, you can chuck the sander into a hand-held drill for better maneuverability.
—Stu McPherson, Truth or Consequences, New Mexico