Here's my recent WNW Sopwith Tripe. On the wing undersides, I first painted the CDL colour. Then I buffed up the surface with a fine cloth which gives a glossier effect on the raised ribs, and coated with Klear/Future to protect the decals. Next the rib tapes and edges were masked, and the powders brushed on using a mix of browns, dark greys, olive greens etc. I got progressively darker closer to the fuselage and on the lowest wing, to represent the effects of being closer to the ground, engine oil and exhaust effects etc. I carried this on to the fuselage under surface.

Build up of rib masking tapes

Here is a more subtle effect on the same aircraft rudder, where I used smoke coloured powders on top of the painted rudder to highlight (or is it lowlight as I was representing the shade?) the rudder structure.

And some rib effects and staining on the fuselage/wing upper surface.
