So far all the models I've painted have been left in pristine condition but in reality railways aren't really clean places. It won't take more than a few miles for mud and dirt to be deposited onto a newly painted surface. I haven't yet been able to bring myself to try and weather one of the wagons I've finished with transfers, but I thought I'd have a go at muddying up the LNWR 1 plank wagon given that it won't be a particularly useful model as I messed up one of the axle holes.
There are a number of weathering products available including paints and weathering powders, but I decided to start my weather experiments using a spray can of Modelmates Mud Brown. I applied three thin coats before I was happy that the blue colour had been adequately toned down. While it isn't perfect I'm quite happy with this really simple approach to weathering, and I feel that the final model is much better for it.