i wash all engines with a pressure washer, simple green, sponges and brushes. things you need to be the most careful around are the alternator and air filter (if exposed). ive heard that on occassion coil packs, distributors, etc. have issues as well. if your engine is in good working order there shouldnt be much to worry about. out of all the cars ive cleaned over the years only "1" has ever had a problem.
there are no guarantees with anything electrical being exposed to water so pretty much youre doing it at your own risk. just use a vacuum and some cotton towels to make sure everything is as dry as possible :thumb:
p.s. on my K&N FIPK i just remove my filter, cover the opening with a piece of plastic and use the clamp to hold it in place. you could also wrap the alternator with plastic and use a rubber band to hold it if youre really nervous about getting it wet.
im downloading the book just for kicks... who knows, i might learn something i didnt know ;D