Melting ice off of trucks fast
Water has a high heat capacity, so I agree with JoeHobbit that a spray of hot water via hose would probably work best. A power washer that is capable of heating the water might be worth getting. A secondary advantage of doing this is that the water spray would remove accumulated road salt, which accelerates corrosion. Short of that, a space heater that blows hot air on the truck would be a less effective but also less messy solution. A moving stream of hot water or air should be far more effective than static immersion.

Small amounts of ice deposits can be removed with an aerosol deicer spray.

See, there is actually a lot of chemistry going on here.