I'm having a hard time imagining you being able to pull it off in ND in December. I always wait for the right temp and overall conditions to shoot. You must have good ventilation, which to me is both garage doors open. As a garage painter myself, I urge you to wait until ambient temps are going to be above 60 degrees for at least 8 hours or so. BTW too hot or too windy will tank your job too. I tried to shoot clear on a 90 degree day with stiff, dry wind, and first, the clear was DRY before hitting the panels, and second, most of it went everywhere but the car. I was using the slowest activator, too.
Lots of stuff to bite you in the a__ when you're a garage painter. Waiting can save a lot of time, effort, and especially money, trust me.