Where I ref we where having problems with rental masks fogging up (single pain). I came across that if use shaving cream on your bathroom mirror it stops fogging (it does).
Well to make a long story short, some of our customers where fogging up on Saturday, so I used the shaving cream, damn it actually worked. It didn't eliminate all of it, but it really helped. Well, they weren't taking off there goggles to see, so I consider that a win. Keep Glass from Fogging Up with a Bit of Shaving Cream