A product in a small blue can called "Never Dull" works great on brass -- and will turn your fingers black too! (But that will wash off...) It smells like it has turpentine in it, and it looks like raw untreated cotton balls -- but it works great.
Some others will go in the other direction, and wipe down all their brass parts with a cleaning patch that has powder fouling on it. Instead of "never dull" -- you'll get an "always dull" dark patina and aged look to the brass -- so it all depends upon what look you want.
Scratches are tougher...
Don't have any suggestions for those, but if they're too deep and you file or polish too much/too deep, you can actually polish in a "creek bed" or depression where the scratch (the "creek" itself) used to be... It too will be visible, although maybe not as unsightly.
I'd bet the powder-fouled patches and the old/antiqued-looking patina would help to discolor and HIDE the scratches more than they'd show on a brightly polished piece though. Find some old brass keys, scratch them, then treat each one differently to see which hides the scratches better, and to see which "look" you like better.
Hope this helps.
Old No7