Here is a trick that I use. Buy a bar of glycerine soap from Walgreens or your local store. Cut chunks of it into a small 35mm film container (for those that don't know what this is...this is what was used before digital photography). Place the container in the microwave for a short duration and it will melt the chunks into a mass. Now, you simply moisten your finger with water or saliva, rub them on the soap, and then rub that on the glasses. It is important to let the THIN film of glycerine soap dry. You dont need a thick layer, thinner is better. As soon as it dries, wipe it off with a soft cotton towel (cotton diaper clothes work great). Do not use a paper towel. This technique is quick and works. You can literally do it between stages if necessary.