Brass wheel brush in the Dremel tool is safe and effective for cleaning the deposits out of the corners of the groove. The abrasive rubber wheels then can be used to remove a tiny bit of the surface and make it shiney. The bore can be polisjed with felt buffs but they cut quicky so go easy. The cotton bobs and buffs on die grindere shafts (1/4“ normally) can be used in 1/4 drill or 1/4 shaft drive. Just don't buy cheap brass wheels or you will buy 3-5x as many as a good quality dremel brand, or areputable place that does polishing supplies.
CAUTION: most wire wheel with 1/4 shafts are brass coated Steel wire brushes. DO NOT use brass coated steel wire brushes or steel wire brushes on the inside bore. They are too aggressive and like TT says, not recommended.
The rubber abrasive bits are good to use on corners of the exterior that are hard to reach with buffs. Then lots of time with hard felt buffs in those corners to blend it out to where the buff can reach.
Strip the paint before buffing then polish to even sheen with sandpaper from 400, 600, 800, 1000 if you want a mirror polish. Then you use your brown, white, and blue polishing