First thing to talk about is that stainless is a much harder metal then aluminum. My process is pretty much the same for both with minor adjustments when doing stainless.
If you're doing a small area or piece that's in good shape with no pitting or scratches you can use a DA sander with 320, 400 and 600 grit aluminum oxide sand paper.
If you're working on a large area or badly pitted, scratched pieces I suggest using a 3000/3500 rpm polisher with a foam backing plate you will save a TON of time on your sanding process. Here's a pic of the foam backing plate I use.
Use 180, 320, 400, and 600 with the 3000/3500 rotary polisher then if you choose you can DA with 600 grit as a last step to smooth out the surface even more, and make the polishing process easier.
Polishing stainless must be done at 6000 rpm any slower will result in leaving sander marks and any faster can result in burn marks. Polishing stainless is done the same way as aluminum the only difference is time, you need to be patient, give the 439T Green Menzerna bar time to work you're travel speed will be slower to make sure to remove all the sander marks. Then finish with the 480BLF Blue Menzerna bar.
here's a Video of me polishing some straps on a Peterbilt
if you have further questions post them here or send me a PM on Facebook
thanks for reading and I hpe we can do business in the future.
Denis - Owner, Master Detailer