[Blue_Heron]

Tucker is right. Heat from combustion, even clean combustion like propane, produces water vapor as a byproduct. You'll get the temp up, but it won't help on the humidity. You might try some inexpensive electric space heaters. With electric heat, as temperature rises relative humidity will drop as you get the temperature farther above dew point. Might be difficult to keep heat up and keep the shop well ventilated for spraying. Should be less of an issue if you plan to roll and tip.
Dave