Spray from the front, make sure engine is cold, no point shocking hot exhausts.
Mine gets filthy humongous amount of bugs on it at the mo'
If worried about the engine bay a leaf blower works wonders you ideally would need bonnet stays though.
Do you drive your car in the wet? if not why not? where do you think rain and road spray goes?
It's just a car treat it like one and not some fragile toy.
