I’m actually ok in my garage without heat BUT just read the label on Arm R Seal and it suggested 70 degrees or higher.
I’m Norcal Bay Area and my garage will be 50s to 60s for the next 3-4 months likely. Applying any finishes will be tough.
I was bout to fire up a 125k btu propane jet type heater. It has a thermostat. Read that it might not work.
Garage has a 20ft long ridge vent if that helps.
I’ve looked into 110v 12-15amp infrared heaters too. Those seem more of an object heating than room heating.