Been cold as a witch's tit in a brass bra out here lately. I picked up a small kerosene indoor-safe (?!) heater. I'm not sure it will belt out enough heat, but it should be good. Except the cold air blows through that garage like the walls aren't even there.
Hopefully the heater will do the job. I'd hate to have to put things off until the weather warms up, but it's just too darn cold to work in that unheated garage.
The unit I got was the small 10,000 btu DynaGlo heater, from Lowe's.