yes, rainX is a very bad idea. It weakens the lenses. They are very similar paintball lenses and for rentals they freak out on people that bring RainX from home to do it because it destroys them
that guy mark is hilarious. my trick to no fog is taking goggles off my face on the way up. If hiking they're in my pack, at the resort I they chill on the brim of my helmet (which is also another reason to wear a helmet).