Beautiful build on this model, that thing must be huge in 1/32 scale! I have a friend that picked up their new Mustang as well is there Japanese aircraft (the name escapes me at the moment) and says they are fantastic models.
That plane did leak all you like a sieve and could be pretty well covered, but the Navy also very quickly cleaned the plane up after a flight, so I would guess how much oil you show would depend on whether it was before or after a flight. Or even eight engine run up before a flight.
I have been playing around with a pastel wash on one of my Klingon models, I scraped a number of different colors from the hard pastel chalks and then mixed it with water and Future. I have seen videos where people would use the pastel chalk with just water and after it dried, they could get it to come off fairly easy with either a Kleenex or a dry paintbrush. I couldn't, then I started using a dry toothbrush vigorously and it was coming off very slowly. Then I was using water on the model as well as the toothbrush again going over it vigorously and while it came off better, it was still coming of slowly and I did find I could control it, although I think it would take a lot more work to get it completely off. I used the Future to help break the surface tension of the water which it did, it went down beautifully with no beading up, I was hoping that the Future would make it a little more resistant to coming off, it worked a lot better than I thought or even hoped, in fact some ways, it worked too good as I discovered the entire bottom of the model, when I worked on it more, I'll carefully put it into the large areas between the raised panels and then carefully put it on the raised areas where I want it removing what's needed before it dries completely.