In the real World, deglazing cylinders and "surfacing" them after they come
out of the boring-bar (bored out to a larger size) is done with stones at
around 220 grit. We used 180/220 where I worked. The one with the balls
of abrasive (on the left) is called a bottle brush.

http://www.hastingsmfg.com/Service%2..._deglazing.htm

This is a good article about deglazing. The ball type stones have an added benefit
in that they radius the edges of the ports to help keep the rings from catching
on sharp edges. You run them clock wise, then counter clockwise with the
drill motor to catch both sides of the ports.

FBD.