I've been using a solution of distilled water and whatever comes off of my fingertips when I'm fishing the coin out..
I started cleaning junk LRB, and had the same basic experience as TIF. I still have 7 or 8 soaking, I'll get them out every now and then and clean a bit, just kind of fun to do. I just remove dirt, I'm not brave enough to go after hard deposits really. Distilled water, tooth picks, tooth brush, a needle...that's all I use. here are some that came out ok... BEFORE... AFTER... pretty low quality coins, but they did improve...except the one on the right. this is about as good as you can get from uncleaned lots. here's one that came out the best from a lot of uncleaned coins, I was very surprised to find a decent LRB under the junk instead of a worn slick slug.