In the final stages now. The last bits of weathering are now done, and here's how I did it.
First, the roofs. I had already painted the roofs in a flat "roof" grey.
To add a bit of life, I patch-painted a slightly darker shade in various places as if there had been running repairs undertaken at some point.
I followed up with some random dry-brushing of a dirty black and brown mix, although it was mostly black.
I disappeared into the loft to wield the airbrush and get a sooty mess over things.
Finally, some selected dry brushing, and a bit of dirty thinners, was applied to give streaks, as if the dirt had been rained on for some time.
After carefully cleaning out the interiors again, I reassembled the models, complete with the bogies which had been given some further weathering with oil and rust effects, and started the process of adding grime to the bodies.
As explained previously, I was after the effect of grime in the nooks and crannies, after the sides had been cleaned by the mop and bucket method. I've assumed mechanical cleaning plants weren't commonplace in the mid-1950s.
I dry-brushed the black/brown/orange mix around handles, hinges and door bumpers, then cleaned back with a clean cotton bud dampened with white spirit. Sometimes a gentle working with a clean brush was required to get dirt out of a corner where it wasn't wanted.
I dry-brushed around the bottoms of the doors, and along the bottom edge of the body, again cleaning back with the image of someone wielding a mop with noxious chemicals on the damp end. I let dirt remain where it might not be reached by the cleaning.
This shot gives an idea of the bogie weathering. Overall, I am pleased with the finished result. It's not filthy, but neither is it ex-works.
Satisfied with my efforts, I packed the coaches carefully in a box, and cleared the workbench for some photography. I'll post the results over in my gallery thread.
I've enjoyed this build. I've learned that I won't ever use Fox transfers for lining ever again, and learned a lot more about the prototype - which is never a bad thing. I need to improve my painting skills, as things didn't go quite as planned at times, but the finished coaches look smart in their carmine and cream livery.
Next, back to complete the LNWR motor train coaches. Around Christmas I shall start the Mk1 RMB and the 57xx, which should see me occupied for the first couple of months of 2014. With luck, some more commissions will come my way in the meantime.