Heres how I do it. I cover all sensitive electronics and disconnect the neg battery cable first. I then spray a heavy amount of megs APC undiluted. I don't use water first. Then I use various brushes to gently scrub everything while spraying more APC. Once I'm satisfied I do a low pressure rinse with water. After the low pressure rinse I wipe quickly to just remove the big concentration of water. Then while there are still water spots everywhere I spray megs hyper dressing all over and wipe down. Totally time takes roughly 20 min from start to finish. The after pics aren't the greatest because of where the sun was at so it doesn't do it justice.
Meg's super degreaser at 4:1 for really nasty stuff, 10:1 for clean just dusty engines. Bag up major electronic components, and be gentle with the water for rinseing. I bring engine up to temp to help dry it a bit, them use Meg's water based dressing. Let air dry.