A bit of pre-WSM weathering....I know D233 is way too early for PMB but as my Dad served on CP's liners and freight vessels it may get an outing....
and you can never have too many Class 37s.....
Just a bit...I quote from the BBC Good Food (yes really...) website...
"It's made with equal parts of vodka, gin, tequila, rum and triple sec, plus lime, cola and plenty of ice"
If you did want to reproduce that it would be relatively straightforward.
Airbrush the grime on and then "clean" the relevant bit of the loco with a minibrush, a cotton bud or paint brush moist (but not wet) with the appropriate thinners...mimicking the movements made by a cleaner - it could be a long handled brush done from sleeper level with some of the yellow panel also cleaned for better visibility as well as the headcode box?
I've just completed a laser cut card kit by MMR models of a Type 15 signal box. Very pleased with the kit (and email support). I prefer mdf for brickwork but the card in this kit works well with the timber prototype.
ChrisH
This may help - my first attempt in 7mm now sold. I'm looking at something a little smaller in 7mm using cut down Setrack points so I can keep some of the stock - most of my smaller locos seem quite happy running over it..
Chris H