You need to go with lighter colours on dark blue. Exhaust stains show up as greyish brown, panel edges get highlighted with wear making them lighter. It's a little counter-intuitive but a light coloured wash will help to make the panel lines stand out a bit. You can also vary the panels a little with shading the blue so it isn't a solid shade.
You can also try the dot filtering technique. See page 8 of
this build. Actually that entire buld is an incredibly inspiring textbook on how to do a Navy aircraft.