There is nothing more difficult than detailing a Chromed Out Harley IMO!
For a show car underhood I recommend Cycle Wash followed by a electric leaf blower etc. Cycle Wash is just Amaizing stuff!

If you are cleaning a daily driver then the Simple Green/White Wall cleaners types work very well. I just don't like the wax stripping they do. It's pretty strong stuff and I wouldn't like to get it on my paint.
Newer cars, ONLY when cold. Older cars, warm seems to work best and yes, water in the distributor can be a bother. I don't worry about the starter, carburetor, wiper motor or the alternator, wash away!

Common sense, the least common of all the senses.
Mom.

For fear of ridicule, society stifles creativity.
Ricky Valdes