I never had luck with the chemical packs til this season. I picked some up in Vermont on a whim and they worked great! I was surprised because in the past they never got "hot" or even slightly warm? They don't do well if they get wet either?
I am also looking for a way to keep the toes on my feet? Tried doubling up wool socks to no avail it just cuts the blood off even more being stuffed in the boot and gets colder?
I am now looking into the heater body suit, the big boot covers, and a new pair of boots. I hunted in near zero weather all this week and the only thing that got "frozen" were my dang feet.
Years back those chemical toe heaters used to work really good, I think these days they cheap out on the ingredients and they rarely work at all.
Wear wool socks, merino wool if you can find them...and use a dry anti antiperspirant on your feet to reduce sweating. It also helps to put a wool insole in your boots to protect you from the cold coming through the soles....