Rusty bridge sides

 I don't know what the bridge sides would have looked like at Selly Oak in the 1970s, but rusty seems a reasonable bet. 

Red oxide car primer is a good base colour for this work and will show up anything too horrible with the modelling. 

After that, I opened up the Lifecolor Dust and Rust pack of paints and splodged the three darkest colours randomly everywhere. The paint was thinned a little by dipping my brush into some water every so often so the colours blended. It also makes the paint go further, 'cos this stuff isn't cheap. 

One fully dry, I'll admit to being really pleased with the effect and I was tempted to stop there, but decided the bridge would probably have been painted, but that paint would be peeling off. 

 So, out came the hair spray, giving everything a good, thick coat. That was dried with a hair dryer and a coat of grey spray primer applied. 

Next, the grey was scrubbed with a toothbrush and plenty of water. Sometimes the paint stuck well, in other places it gave way to reveal the rust. I think it's looking pretty good, you just have to be very violent with your carefully built model - that's the hardest thing!