[Special Coupe Frank]

Personally, I wouldn't use any spray stronger than a garden-hose... and proceed carefully around windows / doors, roof, rain gutters... try not to spray "up into" places...

Once you get an idea of how watertight your car is, you might get more adventuresome.

I see many pre-War cars ( some are restorations ) with water staining on the headliner around the edges and on the side panels and seats from water infiltration... if you've invested big bucks in a cloth interior, you might want to keep the hose away from the upper parts of the car ?

Mine is just an old driver, so I'm not afraid to turn the hose on her...