I would suggest taping off the engine area with plastic sheeting so you can use a hose (at low pressure as Gilles mentioned) without worry about getting it inside the car. I also covered any exposed electronics with plastic and tape, they should be waterproof, but why risk it. I cleaned my engine using simple green and a brush, then I put 303 on the plastic, last time I took the engine cover off it still looked pretty good.
Porscha
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