Legolas, I had to chuckle. A week ago Saturday I was sitting in the piney woods not moving a muscle. It was 8 degrees. HA! I was shivering to beat the band, and my feet were blocks of dry ice. The sock trick works! I never thought to use socks, though. Spare hat and neck gaiter, one on each boot. Makes quite a difference. I didn't have hand warmers that day.
The more air that comes into contact with a chemical warmer, the faster (and hotter) they combust (oxidize). They won't last quite as long, but they give a lovely heat.
Killdeer