I have a lot of experience polishing metals over the years. It is simply taking a finish thought a series of finer and finer abrasives. You start with what ever is the grit that will make the metal smother than what it is now, all the way to at least #400 grit. Then you move into the buffing compounds till finally you arrive at the final polishing compound! I am sure you will find lots of stuff on the web if you start searching. Here is the first one I found on Google.
http://www.perfectpolish.com/PS it is very time consuming work and you need some high power buffers. Also you can burn edges that will cause cases not to seal if you are not careful!
Alan
