I spent a fair while yesterday working on the MTA underframes with powders, plus painting a few details and doing a little drybrushing and black wash for fake shadows and highlights. I think the drybrushing may have helped to lessen the overly soft finish, since it sharpens up the edges and also puts a bit of fine flecked detail on the panels. I've also cleaned up the data panels/overhead flashes a bit more, painted the shiny grab handles, touched in the buffers again, and rusted the steps and grabs lightly. See what you think:

On the really dirty one I took the 'camouflage' (it was Tamiya DaK dark yellow, so a very apt description!) back to clean paint and re-did the mud splatters with a thick mixture of pigment and white spirit to get some texture. I then picked away at any blobs with a cocktail stick to try and get the runs vertical - looking at the pictures this might need another 5 minutes attention.

The mud is also carried onto protruding parts of the underframe (as per the prototype picture) under the heaviest spills.

I'm pretty happy with these now (although not with the photos - too much bloom from the backdrop - if I get some decent outdoor light I'll try and take some better ones) so I don't think I'll do more to the outsides for a while unless anyone has any bright ideas. The insides need tackling still - I want to try Pugsley's method since the results look amazing.