Ducting from the outside would be more difficult than it's worth - for me. So, I'm going to bite the bullet and use kerosene in my heater and use it to pre-heat before painting and maintaining temps between coats. Fortunately, it's not really cold here, 40s at night and low to mid 60s during the day. Heater and laser temp gun should be arriving from Amazon today.
its definitly a better option for placement since the overspray wont interact with the open flame since the force of air is pushing out through the ducting and you dont have to keep lugging it inside and outside of garage inbetween coats. all i did was unplug the extension cord a few minutes before spraying. and i would alternate systems- exhaust fans on during spraying then shut off when overspray clears out then turn heat on, that way i was able to keep a constant 80-90 degrees in garage during the freezing winter months