I built a Sam Devlin design Duck boat in Port Angeles, WA in the winter in an unheated shop in about 1995 and used System 3 epoxy. I connected two 8 ft 2x4s end to end and hung them from the rafters with ropes & pulleys and mounted 6 heat lamps evenly spaced on them.
I'd lower them to about 6 ft or so (shop had a 14 ft open rafter ceiling) while working on the boat - to keep myself warm, then lower them to 3 or 4 ft (can't remember - it was 25 years ago) and leave them on for the night to keep the epoxy warm while it cured.
It worked like a charm. I spent some time at 1st checking temps at various heights, so's not to under or overdo it or start a fire.