I did my E-Zero engine compartment last month before the Saleen show... came out very nice (see below).
I wrote a dissertation about my procedure after I got my car a couple years aog and posted it at
www.waxforum.com. You can see the post, with pictures, here:
http://www.waxforum.com/showpost.php?p=1846&postcount=12
The only difference I did this time was after I used a mild degreaser and agitated greasy areas with a small brush, I used a car wash solution in a spray bottle as a "pre-rinse" before rinsing gently with a hose. I also kept the hood up and was sure not to soak it too much with water, and let it "drain" a bit before I later dropped the hood.
Then after my rinse with a hose, I diluted my Mothers Protectant with filtered water so it was a 50/50 mix and put it in a spray bottle with a fine mist setting. I sprayed everything, including the hood insulator. Then I ran the engine.
The whole procedure took about a half hour.
Now I will admit that this time I got a "Check Engine" light for a couple of weeks, but it finally went out.
About the only thing it needs now is a new oil filler cap and my battery terminals cleaned-up.