I used a phosphoric acid (diluted) solution that is made for welding. Just about any metal cleaner/degreaser that is made for welding prep are usually phosphoric acid based, so any welding supply store will have a similar product. I get mine from Industrial Metal Supply but they don't have those stores where you are on the east coast.
CLR will remove rust, bust it is no longer phosphoric acid based (maybe that's just California?). Anyway I like to use these types of cleaners first before moving to polish. For example, if you are a motorcycle guy and ever tried polishing chrome or stainless headers that have 'blued' or otherwise discolored by heat, use any phosphoric acid based solution on a sponge, nice and wet... after a few sponge downs the discoloration is gone and then use Blue magic polish. Save hours of elbow grease. For small parts, you can soak it in the stuff overnight and it works wonders.