There are also products made for scuba diving/snorkeling that are excellent in keeping the mask free of fog. They're inexpensive, maybe something like that would work. I've used the following Sea Gold Anti-Fog and it works well: http://www.scuba.com/scuba-gear-54/028053/McNett-Sea-Gold-Anti-Fog.html
The trick in using this gel is to apply a good layer, then quickly rinse with fresh water, and it leaves a crystal clear film that does not fog.
Also, in a pinch, I've been told that you can simply spit in your mask, rub it around and that will keep it from fogging. Divers swear by that, but I have not tried. Maybe spit on your cam & let us know how it works?
I've spent countless hours either on my hands and knees or bent over, messing up my back, looking for blood. One such instance I remember most was a hog hunt a few years ago in Mississippi. I had never shot a hog so when I poked a hole in this guy; I was determined to find him. Wearing snake leggings, I crawled on my hands and knees through the briars and the brambles and bushes where a rabbit wouldn't go. I found a spot of blood here and there but never the pig. And lucky for me, I didn't find...