Dremel is going to do little more than frustrate you.
If you've got surface imperfections that you want to work out before final polishing and you don't have a proper bench grinder with sisal or buffing wheels; you can go to any auto parts store and get a variety of wet sanding paper. Use a rigid block and not too much pressure. Work it from 800 on up. You'll be able to get it to shine pretty well at 1800-2000 without any polishing compound.
Then use Flitz metal polish!
The polishing compounds you'll get with your Dremel aren't that great in the first place and they're dependent on the metal you're polishing and the speed you're polishing at. Unless you have a bar of "Black Magic" or fine "Cut & Color" and a 1" or wider buffer, it'll be tough to get that consistent mirror glaze and make it last.
The nice thing about Flitz, is that it has a component that slows oxidation/patina from developing on the ferrous metals. Once you get the surface to the right natural shine, Flitz will do the rest.
*I've not fooled with anything in my shop in months so I may have forgotten how to do it properly. I have 4 buffers (2 bench grinders with 2 wheels each) and I use liquid (clay) applied abrasives on several wheels for removing material, and sisal and sewn buffing wheels on the others with different compounds depending on the metal I'm polishing. Then I have a soft cotton polisher I use on my drill press with a secret recipe and the aluminum, brass, and nickel look wet when finished, if that's the look I'm going for.