Just a quick FYI - I went riding this morning (25* or so) just to get the bike fired up for about an hour, and got a chance to use a sample of FogTech Anti-Fog Solution that I picked up at the Cleveland Bike Show. My helmet fogs up very easily.
It worked great. I don't know how long an application of this stuff will last, but it does work better than the Scott Fog Wipes or the Cat Crap I was using.
I'm sure PinLock anti-fog lens inserts are probably the best overall solution, but until then.
EDIT: Do you exchange shields with the insert in, or just remove the insert? I guess what I'm getting at here, is whether or not the inserts are designed to be removed and reinstalled, time and again?
I swap inserts, but I am only going on a couple weeks with the Pinlocks. My only complaint is I feel bad when I flex the shield as far as I have to, to put the insert in. I will never go back to riding in the cold without one.