I reckon it's a worthwhile thread to sticky/pin actually, never mind delete
A lot of my players at FireFight have fogging problems with their paintball masks or shooting glasses - and motorbike antifog doesn't always work.
We never did figure out why not - Perhaps some people's sweat / breath condensation's just not compatible with the brand?
Anyway, some other solutions include:
Washing up detergent, wiped across the lens and left to dry.
Lemon juice - likewise.
I'm sure other folk use other things... One guy swears by spitting in his mask!