During the day, I'll ride at street-traffic pace with the shield cracked just a bit. This will subdue the fogging while moving and stopped. However, I use a Scorpion EXO-1000 helmet and at freeway speeds, the vents do just fine to keep my shield from fogging. I've seen chemical sprays that say they keep your shield from fogging, but if it's as "good" as the factory spray that they say they put on the shield, I wouldn't use it.yeah, i have to crack my face shield to keep mine from fogging up.
if you are moving fast enough, some helmet vents will keep it clear,
but i basically have to raise mine BEFORE i get to a dead stop