Hi All,
Hmmm acetone does not sound like a good idea, as it might damage the coating on the lens. I carry little packets of 4 ply tissues, one of these dampened will remove dirt if used carefully with out damage. About once a year I used a little liquid soap in the same manner to remove any built up oily residue and a wet soft cloth or one of the tissues to wash it off seesm to work for me
