I did have a small "bullet" heater which worked, but after a while my eyes would begin to sting, and the humidity it added to the inside of the garage was considerable. And I could hardly hear myself think, it's like a jet engine! But it did the job, sort of.
Now I finally have an outside-air ceiling heater. It works well, is much quieter, and I don't need to worry about pulling in woodworking dust or engine exhaust, though the outside combustion air option was expensive. It's rated for 65K btu, I only use it occasionally, and it's connected to a 100-lb tank.
I suspect, however, that if I used it on a regular basis the 100-lb tank would be too small to last longer than a few weeks. The garage is 32 x 32, with 2x4 walls; ceiling & walls are insulated & covered.