Once the cleaner/degreaser has been sprayed and left to dwell for about 5 mins, I've found it useful to agitate the chemical with a 2 inch (1 inch for smaller nooks etc) soft bristle paint brush. It's generally not as aggressive to the paint and rubbers as rubbing hard with rags. After agitating, you're ready to rinse. I don't imagine you'll need a PW for an 8P engine bay unless you've had the bonnet open while it's been raining mud!!! A normal hose spray should be fine.
Before you put any liquids near your bay (degreaser or water) make sure you put silver kitchen foil round all electrical connectors and that it has been 'compacted in'. Also, the air intake and MAF should be blocked off from liquid intake.
Once rinsed, dry the bits and finish by applying a good dressing like 303 Aerospace Protectant (this does all parts).
As AudiLad says, G101 is a good cleanser for this purpose, but you may not get a hold of it easily as the area sellers deliver to companies only, so they've told me. Polished Bliss on here sell Meguiar's Super Degreaser which is good for the engine bay. I've still got about 3/4 of a bottle of AG Degreaser which I've found to be up to the job also.
I take my hat of to AudiLad for getting into the bay every time he washes his car
Have fun. :icon_thumright:
PS There's a Polished Bliss guide on bay detailing
