Assuming you're wearing the helmet for takeoff, once you're above 1,000 feet, take the helmet off until you're getting ready to jump. Keep the visor open until the last practical moment before exit.
I find doing those two things significantly reduces any fogging I might have with my full-face helmets. It seems like if I do have fogging light and it's at the end of the skydive, and since I open my visor under canopy, it's not a huge deal to me.
I've borrowed two. The XL I 'thought' fit just fine. but it fogged like crazy - even after exit I did one four way pretty much blind the whole dive. It went well. - I did everything NWFlyer recommended - still no good.
I borrowed a L from a friend and found that it fit near my mouth and nose much snugger and allowed me to just breath through my mouth.
They actually seem to be sized pretty small. AND, they have a lengthy break in period. A new L is very tight and not comfy at all for me. But once broken in, it fits me very well. Something to think about or see if others have discovered the same.
(This post was edited by rehmwa on Sep 11, 2012, 1:39 PM)
i jump a cookie gas1 and you cant open the visor, and i hate waiting until its go-time to put on the helmet, so i just got some rainx antifog wipes, one wipe on the inside of the lense is all you need, it usually lasts close to a month