Make sure the engine is cool. I spray down the whole engine bay with simple green, let it soak in for 5 minutes or so. I then take the hose and put it on the shower setting and spray off everything, staying away from the alternator. I then take my air compressor and blow out/off all standing water, blow out all electronics, make sure to get any water out of the intake valley area, etc. Then I start the truck and let it run for a couple minutes to clean the belts off and burn off any residual moisture.
My go to engine bay detailer is Stoner's Trim Shine.
2013 Silverado - Ext. Cab - Z71 - Mocha Steel Metallic - 5.3L - 4x4
Zone 2" Level - Airaid MIT- 5000k HIDs - Debadged
Black Bear Tuned - 285/65/18 BFG KO2's - MBRP Exhaust