If you go back a few posts, citric acid is what was recommended. I used one of those squeezy lemon 'Jif' juices with a cotton bud/swab stick. Last year I used Isopropyl Alcohol on a dial. It worked a bit too well and stripped it back to metal. You could try alcohol diluted and be super careful.
Sorry if you said already (I'm new on this thread) how did you clean the dial?