I can share some tips w/ ya. I've only really detailed the engine bay twice but it is pretty darned clean. I let her sit a few hours to cool the engine down first. I left the battery connected and left the battery cover on. I used a 20-80 mix simple green:water and sprayed it on the inside of the engine (not on the paint on the firewall and not on the plastic/rubber on the outsides )careful not to get the plenum, not sure it would do to that metal. Let it sit for about 10 mins or so and just hose it down. I rinsed out the brake fluid area w/ just water. Then I used a yard stick cut in half wrapped wrapped w/ mf like a swab to dry/remove any dirt left, from the lower parts and the firewall area. (Also used this technique to use my quick detailer on the paint back there) I guess to really get it good down in the lower part of the engine bay you could go in from underneath, but that's a pain. I use Aerospace 303 on all the rubber hoses and plastic parts, and gaskets etc. If you spray it on a sponge (I used a sponge paint brush 1 1/2 inches wide) to apply it and buff it off it leaves a nice matte finish. After you detail it once it really is easy to keep up. The only thing that I got dinged on in points in my engine bay were the pulleys, I was afraid to mess w/ them so I didn't. Maybe DaKing could give some advice there....
Hope that helped....
Hope that helped....