In 8 years of using a shotgun scope on my turkey gun I never once had the external lenses fog up. Well a few days ago was hunting in heaviest fog I've ever experienced while turkey hunting and my scope lenses fogged over and thank God I had both a lens cloth and lens cleaning wipes to fix it but if this happened with a Tom fast approaching I could see it costing me a shot.
I have never used anti-fog products so I have no idea if they work or not. Was wondering if anyone has one they know works and can recommend.