i hunted Cohutta once in the winter in a popup with no heat. During the night a cold front moved thru, and we had a heavy fog. The next morning, we got up and the fog had frozen to the side of the trees from the direction the breeze was blowing. It looked like a young snow everywhere.
We had a Coleman fueled catalytic heater that had a mushroom shaped dome top. We fired it up, and the 4 of us sat around the table with it under the table. We draped a sleeping bag over the end of the table to make the heat come up by us.
Yup I have a mr. buddy propane heater in my pop up with no electricity. It works fine. With a decent bag and wool socks it will keep you plenty warm enough. Make sure you have a carbon monoxide and smoke alarm in your camper for safety.
A electric heater will heat one great too if u have electricity, we had a fellow in our club that camped in one, he left it up all season do he took tarps and covered the ends/cloth, used small clamps to keep it on. And used a small electric heater, worked great, by the way u can generally put gas heat in one for 500.00 and that's a new unit, I've had one done before