Coincidentally, I polished up my brass mailbox this morning. I should have taken a "before" photo but I forgot. You can get the idea of how badly beaten up and tarnished it was by looking at the side of the lip near the hinge screw and the edge that runs parallel to the wall.
It took about 10 minutes to bring it to the state you can see in the photo below.
Step 1. RO125 in rotex mode with granat 500 and interface pad. (I tried starting with platin 1000 but wasn't making any headway so I stepped down to granat 500.)
Step 2. RO125 in RO mode with platin2 1000.
I'm not sure about the dust that sanding and polishing brass creates and associated safety issues, but as I didn't have my CT with me I did wear a respirator. My hands were pretty black afterwards.