If you work in cold weather like me you probably get irritated when your welding hood, goggles, or face shield fog up. To fix this i bought some Rain-X "Anti Fog" the kind you use for car windows and put 2 or 3 coats on . The bottle costs like $1.60 at Walmart and it works like a champ. By the way this wasn't my idea i read about it on a welders forum.
I used to use shaving cream (the foam type like Colgate or Barbasol; not the gel) on the sheild of my full-face motorcycle helmet to keep it from fogging. Just apply a thin coat and wipe it off. It's cheap, works great...and smells good.