"Polish" how? Do you want to take the brushed finish to mirror? Do you want to restore the factory finish? Are there any deep scratches or dents that need to be addressed?
Use some fine 3M Scotch Brite Nylon Pads to achieve the shine you want then use some polishing liquid like Flitz to clean & bring out the luster of your unfluted stainless steel cylinder.
After getting the finish the way I want it, I use Renaissance Wax to put on a shine & protect it. It's non abrasive & I use it on all my revolvers whether blued or stainless. Great stuff.