If those are what I think they are Mal they are used with abrasive paste or lapping compound. The grit imbeds in the lap (soft copper or brass) and it polishes the harder metal in a bore. It won't work in a soft material like plastic.
You can take a dowel or rod and cut a slit in it to wrap fine sandpaper in to make a simple flap wheel. When spun with a drill with some favorite lube the paper will spin out and polish the side of the hole.
I know Micromesh make polishing swabs (something like a Q-tip) that should work especially for the end of the hole.
Slow typing on the phone gives you the answers by others as usual. ;)
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Last edited by Curly; 03-09-2017 at 09:17 PM.