You can look at original brass parts and see tool marks to help determine what was originally used in the finishing process. File marks are VERY common. The idea of a chrome bumper polish is entirely modern. Who knows how well maintained original brass was. It probably varied widely. Sort of how clean a car or house is kept.Was brass furniture originally highly polished, and what we see today is accumulated wear and fine scratches? More importantly, would you know what was used to polish brass?
Me, I go to 600-800, then use #0000 steel wool. Anything finer and it will show *every* little scratch and fingerprint.
Dittos on the buffing wheels. I learned that the hard way.