Generator Compartment

I've seen a few generators and gas powered welders damaged because someone decided they needed to be cleaned. Before getting much water, especially high pressure water, around the generator I would wrap that thing in enough plastic so I knew it would stay dry.

My compartment is lined with a foam and vinyl sound deadening. Not sure how well that would stand up to high pressure and a lot of strong chemicals either.

What kind of mess do you have? If it's really bad you might have some leaks that need attention.

Well there are 2 things, the compartment itself and the gen. I would clean the compartment with whatever works, degreaser etc. However I would not use a high pressure hose or degreaser on the gen itself. Maybe spot cleaning the gen with something on a rag but I would hesitate spraying it down with anything (water or degreaser). I was told by Onan never to spray with degreaser. The seals on the board will totally degrade. Mine is newer though and have no idea what yours is.

Depends on how much oily material.
I normally go to the local car wash, use the engine clean setting to spray with de-greaser and then wash it good with the soap, then rinse good.
I have a small pressure washer here for normal cleaning.
In my old rig I emptied all the compartments and washed them all at the car wash right after I got it. I really had to clean the black and gray water compartment.