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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.
Always do it on a cold engine & I let mine air dry when done. You can use compressed air, just be careful. When I was a kid I did a lot of damage to my dad's car, power washing his engine for him....lol
Wrapping the alternator, etc. is a good practice to apply. Some people use plastic and rubber bands, some use aluminum foil.
I will never use a pressure washer under the hood. Many do without issues but I won't take the chance. The degreasers and products recommended above will work well.
If you're really looking for the "like new" look, McKee's Trim Detailer works great. This is my 2007 Solstice: