Usually soap and water will take off dirt and dust stains, and stains from newspapers. Using sponge, not abrasive type pads. Also a regular eraser, that would erase pencil marks, can help take off stains or oxidation. I have not tried bleach, I would wonder if bleach would discolor the paint - so if you try bleach would only try it on one glass and get it dried to see how it works before using on other glasses. Do not use automatic dishwasher, that will fade the glass. Vinegar might be a milder way, than bleach, to take off stains, I have used vinegar on depression (colored table glassware) glass for stains.