I use Super Clean, pick your choice of degreasing solution. Dish soap works reasonably well as it cuts grease.
I spray on and let it sit a while. I then use a pressure washer on everything.
Avoid spraying directly at openings around the air cleaner and not to close around electrical connections.
I let the truck sit outside with the hood up to dry everything out for a few hours after before I start it up. Best to do it on a day with low humidity so it drys well and fast.