What LG said or I use a worn bore brush with a patch coated in Flitz or any of the fine polishes. I do this after I get the ID where I want it. I highly doubt the tiny bit of extra metal removed will be noticed. While I get a nice smooth surface, I'm not trying for a mirror finish as I won't be able to see myself in it anyway....
As mentioned earlier, I PC my bullets and don't want to scratch the plastic after it's cured. It's been working nicely for a few years and will probably out last the rest of my shooting career.
FWIW, I use my cordless drill for all of this. Wish I had a lathe.
I just re-read your post. When I use a dremel on an ID polish or grind, mine tends to either bind or jump when it gets under a strain. I use an oak dowel split (cut actually) in the middle and automotive sand paper slid into the groove in my cordless drill on high speed. I start with 400 and end at 1000 grit. I run the paper wet with a wd40 type of lubricant.
Keep 10-15 fat bullets ready and check your progress with them. I don't reuse them while measuring. Also use a good micrometer, not a caliper. It is easy and doesn't take too long. You can't put it back in if you remove too much. After you get where you want to be, then size those bullets you've already sized earlier.
Last edited by DHD; 10-10-2019 at 11:56 PM.