After hearing about it from a shooter at the range and a little research on other forums I picked up some of the Lemi Shine dishwashing additive at WalMart. Lemi Shine is citrus acid based powder sold at Wallymart and other stores along with the dishwashing machine powdered soaps. It is sold as a hard water treatment to remove deposits from dishes and dishwashers. Web site is www.lemishine.com
While I've tried a lot of stuff over my many years of reloading I've have to say this stuff is really the best bang for the buck! While it won't polish cases it will really shine up newer ones and clean and brightened up heavily discolored ones.
It is not a soap so grease and oils need to be removed first. A little of the stuff goes a long way; I used a table spoon in a quart of water. I mixed it up in hot water but it still worked fine after the solution reached room temerature. It works pretty quick - don't leave the cases in too long or they will take on a copper hue.
In an ultrasonic cleaner it helded brightened and clean the cases really well. I've recommended ultrasonic cleaners before; the Lemi Shine makes them work even better.
A search on the web will yield a lot more info on using this stuff. I hadn't seen it mentioned here so I thought I would post my results. If this is a repeat in the subject please forgive me - I tried to do a search with no results.