Washes for different colors

By a wash I assume you mean something to simulate weathering and fading ? For the panel lines I would use burnt umber,it can also be used for an overall wash to simulate grime.I have also seen a lighter color used to simulate the effects of salt spray.

  I'm just wondering if the burnt umber might be too dark on the white surface. I've used it on some things in the cockpit. Do you know what color was used to get the salt spary effect?

The earth tones are ok for land based aircraft where they operated under either dusty or muddy conditions. For carrier operations I would experiment with more  greys and blacks for grime in certain areas. Salt water and the sun will bleach the darker paint to a lighter shade so light washes over the top areas of the wings and fuse will be good candidates. FSM had an article a while back just on this very same issue using a Helldiver to show the effects of weathering and fading paint.