A word of caution regarding Simple Green. It is known to cause Corrosion to Electrical Components, Corrosion of Aluminum, and Hydrogen Embrittlement to Highly Stressed Metals. It became such a known issue in the Aviation World that its use was prohibited even though some people continue to use it.
Simple Green finally came out with Extreme Simple Green Aviation Cleaner. See:
Extreme Simple Green
Other high alkaline cleaners such as Fantastic and Formula 409 should also be avoided.
What can you use? I really don't know anymore! I personally used Stoddard Solvent for over 50 years but that is now known to be very toxic. The new Extreme Simple Green Aviation Cleaner is supposedly non-toxic. Turtle Wax Zip Wax Car Wash was approved to wash the Main Rotor Heads of my Helicopters. Another cleaner that has Boeing and McDonnell Douglas approval is HydraSolve that is readily available online from Aircraft Parts and Pilot Supplies, see:
HYDRASOLVE from Aircraft Spruce
Before we knew better in the 60s after every landing we'd wipe down the oil streaks from the nacelles of our R2800 Radial Engines using shop towels soaked in Hi-Octane Leaded Aviation Fuel without using protective gloves while waiting for our passengers to arrive. That was SOP when I got into aviation back in the 50s. As times have changed!!
Good luck,
Jim