Rather than have them all look as if they are just out of the paint shop I'm thinking that at least the roofs should be dirtied up a bit... Thoughts, suggestions?
Mmm, sometimes less is more, so it's just a question of grubbying the roof a little, an perhaps the running gear.
On a couple of occasions, I've used a very dilute wash of acrylic grey - the advantage is that if it's not enough, you can add another coat or two, and then enhance with the odd streak of something.
This yellow wagon has been treated like that

This tanker has been treated with Tamiya weathering powders

(sorry, can't find a very good shot at the moment)
