How do you partition your garage with a double garage door and heat with electric heat?
If it's temporary, you might consider rigid foam insulation. Easy to work with, reasonably cheap. Although my attempt didn't work too well as I have a barn that was just too drafty. But in a well-sealed garage, it might work much better. In the end, I found I had better luck tenting the area I was working on and heating under that with a chick heat lamp (or similar). That was for epoxy work. When the boat was upside down, I found I could heat the hull up with a heat source underneath or inside the hull. I kept the epoxy containers warm with a heating blanket,