This stuff is great for the plane belly:
https://www.frasersaerospace.com/product/wash-wax-all-degreaser/
…and the blue stuff is great for bugs on leading edge etc and general cleaning.
no never wash
i just spray some aviation degreaser like extreme simple green or whatever on a cloth and just wipe it.
I use avgas or petrol on a soft cloth offcut to clear the oil / exhaust residue on the belly every so often.
With regards to the engine, I’m reasonably convinced that wash downs with compressed air and avgas lead to a marginal spade connection contact giving me erratic tach readings which took some time to track down.
