Wrap the propane tank with the electric blanket. Do not wrap around the regulator or the valve, make sure they stay exposed.
Secure the electric blanket to the propane tank with duct tape. Try to cover the entire tank with the blanket.
Plug in the electric blanket and set it to medium temperature.
Open up the regulator valve slowly, and not more than you need to. Leaving the regulator valve completely open makes it more subject to freezing. If you need more gas pressure, connect more than one gas tank together to spread the pressure.
Remove the electric blanket when the propane tank is not in use.