Unless it's really cruddy, on a cool engine just spray WD-40 in there and use some elbow grease.
I usually put plastic grocery bags over the air filter, electronics, etc. etc. and use the garden hose in a very light and cautious fashion of where I'm spraying and how much, be sure to rinse the degreaser you use off really well, then let dry. That's what I do.
Compressed air usually helps get rid of the water faster.