Cleaning the commutator on a postwar engine.

This is what I do, to clean the com if Necessary after you cleaned it and still looks bad, note old school way is one can just use a track eraser then with Q-Tips and some 91% Isopropyl alcohol and done that’s it. But if you want to go the extra mile and polish the commutator, put the armature’s shaft on a drill set it up so it’s easier to handle plus safe and use.
1) clean the commutator with alcohol,
2) let dry and or blow it off
3) use 1000 too 3000 grit wet dry abrasive paper.
Now once armature is Securely in the chuck of a drill hit the trigger than make a few passes. No need to press to hard. All you are doing is cleaning and To some degree Polishing the com. Then add fresh new brushes and new Tension springs and Reassemble you done.