A few tips:
Infrared heat transfer works via "line of sight" so you must have
heaters that point to every panel on the car.....a heater on the
driver's side will not heat the passenger side.

You can buy infrared strips at places like Grainger's or McMaster.
If you GOOGLE the term "infrared heaters", several mfgs will be
listed. Note the spelling of infrared for the correct Google response.

mike in tucson