[Zabco]

I've had pretty good results by using Micro-Mesh or Alpha Abrasives finishing films. Come in grits from 320 through 60,000. Packs of assorted grits are commonly available in hobby stores or online. I make a mandrel slightly smaller in diameter than the inside of the bore that I want to polish. Recommend using plastic rod and not wood as the finishing process is done in water and the wood will swell and cause binding. Cut the abrasive films into strips about 1/2 to 3/4 inches wide and long enough to wrap around the mandrel a couple of times. Place film into a slit cut into end of mandrel and wrap around. Chuck other end of mandrel in battery operated drill. I do this under a faucet with a small stream of running water into the cylinder bore to keep the film lubricated and the bore flushed out so don't use a plug in drill. Start with coarsest grit and then run drill at medium speed while pushing mandrel in and out of bore. check appearance of bore surface every couple of minutes and when it appears to be uniformly "scratched" across the entire surface go the the next higher grit and repeat. I usually go up through 30,000 grit which pretty much leaves a mirror finish. Takes a little time but works well for me.