I agree with Scarecrow Boat. Touching a dial is risky. It is so easy to take off a layer or some script. I usually roll some rodico across to pick up loose dirt and or debris. Then if it’s still that bad I might roll a damp que tip across it but never rub just roll. Then dry with another one instantly. That’s the best you will get without big risk but even then with my method, there is a big risk. It’s just an unknown. It all depends on how the dial was punished during its life.