I use Rain-X, the stuff you wipe on the inside of your car windshield so it doesn;t fog up.
I used it when I played paintball, on my goggles (fat man running around all the time means sweat, sweat means hot, hot means steam, steam means I can' t see a danged thing out my goggles)
Now I use them on my glasses and binocs when I am hunting, seems to work decently well