Hora if the car is completly off you don't have to be that carfull as do you not think that water (vapour at least) gets in when its rain heavly and your driving at 70?

A cars temp will go up as soon as you switch it off but not to the extent of getting any where near causing damage as it no onger has a 500 deg C fire at its center.

Most of it is stopped by the bulk of the radiator though. Its still cautious to not spray directly onto connectors though or battery etc.

I would agree with that but wouldn't worry about the air intake unless you point it stright up it most have a bend with a drain hole in to allow water back out.