I have used Simple Green and Oil Eater which I purchased at Costco.
I have also used engine cleaners I have purchased at Auto Parts Stores but they leave a bad smell.
I first crawl under the coach and spray Oil Eater or Simple Green on everything than I open the engine cover and spray from the top, and close it.
I spray from the rear and than I spray engine with water. I than start the engine and I drive the coach for a few miles to let the water evaporate and get the Alpine washed.
I also clean may battery compartment with banking soda or Coke at the same time.