Greetings from Lexington, Travis!
It's CA. After I've turned down to the bushings, I put the tube directly between centers and use a skew held flat to scrape and make sure things are perfectly round. I also measure or just compare with the bushings to make sure the blank is a little undersized and will allow of the build up of the CA. Three coats of thin and ~6 coats of medium ca, applied with the little bags from pen kits on a mandrel. Then i but the tube back between centers and do the same thing with the skew, gently scraping off the lumps of CA. I'll take 320 or 400 mesh sandpaper and very gently wipe it to create a dull surface - not so much sanding as creating some contrast to look for shiny spots, valleys, bubbles, spots, etc. I'll continue going back and forth through the skew and sanding until I've got things all even and don't see any 'defects,' then make another pass with the skew and start sanding to 12000. This process makes sure things are round and even for me - and don't have dull spots or valleys that the sandpaper might miss while polishing. Using the skew to clean off the 'extra' CA came from a suggestion here on IAP, and I consider it great advice
