Some tips...
I've polished all sorts of parts for projects, aluminum, stainless, brass...
If you go to Grizzly.com and get the random orbital sander bonnets, they are okay. Start with prepolishing liquid, then red rouge, then green fine, then high polish for stainless pink. After all that, hit it with liquid car wax.
All of this should be done with separate bonnets for each grade compound. Sharpie mark them before starting. Apply even pressure, but let the machine do the work.
After an hour or so, you should be able to shave in the reflection!
One more thing, use proper respirator and eye protection and wear a painter's cover-up suit. After doing big polishing jobs, you get covered with all the strings from the polishing wheels/bonnets and all the black oxide that comes off.
You will look like a Yeti when done if you do it right.