I sweat buckets and now that it's nearly summer, the temps are in the 70's to 80's. After about 15 miles, pools of sweat pour down my face and totally smear up my sunglasses. I try to wipe them with a handkerchief, facial tissue, paper towels, etc. but all it does is completely muck up the lenses. Only a thorough wash in soap & warm water and lots of wiping do the lens become clear again. How can I clean them on the road? Is there a solvent or something I can squirt & wipe?