Here's a photo of my first effort at weathering a mineral wagon. It's still waiting for new buffers (the plastic ones on the kit broke off during painting!) and lettering.
My intention was to follow Martyn Welch's method of painting a layer of rust, then applying patches of Maskol, painting a grey coat over the top, then picking off the Maskol to reveal the rust beneath before adding some further subtle weathering.
In the end I think I was too random with my Maskol application and it looked more like a cow than a wagon. The subsequent 'subtle' weathering ended up turning into a complete covering of grime and rust so that there is barely a protoype inch of grey paint left anwhere on the body! This wasn't exactly intentional! However, I think the finished result looks pretty convincing - albeit for a wagon in just about the most extreme state of neglect possible!!
Next time I think I'll try the method of applying the grey paint first, then just stippling on rust and dirt over the top to create a softer, less drastic weathering, if possible. I think maybe the way to acheive this is to begin with a shade much closer to the original grey and gradually blend in a few darker shades rather than - as in this case - just wading in with a heavy, dark mix that just can't be blended into anything!
Anyway, here's a composite picture I just made up, where I've superimposed the photo of the model (above) onto a real background to see how it looks - and I'm pretty chuffed (no pin intended!) with the result. Now if only I can acheive a level of realism with my scenery to match this I'll be more than happy.