Clean mine every 6 - 8 months. Some tips and tools:
-Do not get the battery top plate bracket wet....it will rust
Fortunately everything else doesn't
-Remove and hand clean engine cover separately.
-Leaf blow out any loose dirt/debris with extra attention to top of engine and any crevices. You should be left with caked on dirt/grease.
-Cover battery, alternator, top of engine covered with trash bag.
-Light/medium rinse with hose avoiding battery, ignition coils, alternator.
-Avoiding alternator, battery, engine top...spray down engine bay with Optimum no rinse and wax (any version). OR degreaser if extra dirty
-using a tire brush with about 3 inch bristles, agitate dirt from surfaces.
-rinse
-leaf bower to remove water from crevices
-hand clean top of engine using damp MF towel
-hand clean battery with MF towel (using gloves and common sense) and/or disconnect.
-hand dry everything else with damp microfiber towel
-The Optimum no rinse no wax helps to keep dirt from sticking. Easier subsequent cleanings and no smell. I never had to use strong odor degreasers. Safe on paint of course.