I drive the truck around the block a few times to warm the engine up, then spray everything under the hood down with a garden sprayer filled with a hefty shot of Dawn. Usually the blue stuff in case you're wondering. If I've been parked next to a bunch of bowties, I'll use the orange anti-bacterial. LOL I then hit the engine with a good strong pinpoint nozzle, blasting the mud, crud, blood, and beer from wherever it may be. If there is anything left after round one, I simply repeat the process.
I do NOT directly shoot the alternator, batteries, or fuse box, but I don't care if they get indirect spray. If you drive in the rain, spray will come up from the road and through the radiator Doesn't hurt anything. If the batteries are grody, I'll give them some attention with a stiff brush and some baking soda.