Are you modelling the consist right out of the station or after its run? Makes a difference....
I weather the roof of all cars as these got and stayed dirty and didn't have a varnish finish. Trucks, underbody, couplers, wheels are all obvious targets and should be weathered. I like a matte semi gloss overcoat; takes away the plastic look but still suggests that varnish finish. A little weathering on any fixed steps, around doors and on car ends is in order too.
Less is more on carsides.....
The Broadway Limited at the Horseshoe Curve, so, well on it's way depending on the direction.
When they washed the cars, they didn't wash the roof or ends, right? Just a machine that scrubs the sides, yes?
Ok. I think I'm going to mask the car sides and not touch them at all. I'll spray some black and brown on the roof and try for some subtle streaking along the seams and ribs. I'll weather the couplers and wheels/under body as usual.
Pictures seem to suggest that the roof was did not reflect light the way the varnish does.