There's a company called Dri Wash n Guard that makes car wash products.
I have a set of centennials that are older then dirt. Literally the white on them has turned to a yellow'ish over the years either from UV or from smoke. The balls originally came from Hard Times La Habra I believe.
Dri Wash makes several car wash products, including a metal polish, as well as a product called "oxygone" which is a feather scratch remover. Both the metal polish and the oxygone are about as non abrasive as your going to get. I've tried everything to try to get the old centenials to shine up and nothing worked, inluding the aramith ball cleaner. I went out and got two rags and the metal polish and was pretty blown away with the results. It didn't get rid of the yellow'ish tint on the balls (I believe that the UV has penetrated the surface of the balls and it's discolored pretty deep?) but the colors, and even the yellow'ish part shined up like new.

After the metal polish I used regular dri wash n guard spray wax to put a showroom shine on them. I was getting ready to buy a new set of balls becuase they were so bad, but now I can put that on hold for awhile.
I will say the dri-wash n guard spray wax (works very well for cars by the way) didn't work as good as I was hoping in terms of longevity. The upside though is it isn't super slick like Armor All or the like. It's a true coat of wax that is applied. It lasts quite awhile on the object balls, but the cueball only stays waxed for 3 to 4 hours of play if I had to guess. (Which in reality is all I'd expect out of just about any wax?) It's quick enough to apply though that you can do it in between games while someone is racking. Spray on, and wipe off with a microfiber and your done.
I can't recomend the metal polish enough though for the cleaning of the balls. If the balls aren't that bad and just have some chalk marks that won't come off give the oxygone a try. At the end of cleaning a rack of balls don't be surprised if you feel like you have carpal tunnel. I'm a bit "OCD" when it comes to things like that though.
Incidentally the guy that owns the company is a friend of a friend so I think I could probably get a discount for AZBilliards members. If you guys are interested I can make a couple phone calls and find out?
www.driwashnguard.com
DJ