What's the best way to thaw out a car radiator?
You need to get some heat circulating around the engine. To thaw, drape some blankets or tarps over and down the sides of the car and stick a heater to blow heat down there; the blankets not only contain the heat, but they also keep the wind out.
You will then need to drain as much of the water from the cooling system as possible once you have confirmed that the ice is gone; then run some 50/50 anti-freeze and water through it.
To avoid freezing, change your radiator fluid every other autumn. A 1:1 mix of water and anti-freeze gives the best protection against freezing and boil over.
Learn how to protect pipes and cars from deep freeze at WCPO.