I got the roof painted finally. I wanted to spray it but I felt that might cause it to warp so I brushed the silver on. Three coats later I managed to get it fairly uniform. Silver is a tough paint to get a flat coat of. I painted on the side strusts too and it looks pretty nice now. I washed this down with Badab Black(GW) and Delvan Mud(GW) just to remove the stark shine. However getting a flat wash on was harder than getting a flat silver coat. The washes tend to pool a little which caused me some annoyance. I added a few more strips of plasticard on the corners of the roof as it didn't look correct without them. The biggest problem I have had with the building is the fact that it has evolved so much since I started building it. I wasn't sure how the plasticard would work and I have learned a good bit by using it for this project.
Once the washes were dry I started with some rust. I think the technical term for what I did was adding a filter. Its not really something that you can do on smaller models and I have only seen it done on tanks and railroad carriages. I mixed some red pigment with turpentine. I washed this on quickly over the entire surface. It gives a really slight rust colour across the whole surface. I repeated this about three times using a hairdryer to speed the process up. There are a few spots where it it a little thick. This is because my brush picked up a little too much of the pigment. This happens as the pigment settles quickly to the bottom of the container and if you dip the brush in and hit this layer it picks up a huge amount of pigment. It came out fine but I would have liked it to be a little more subtle.
Now I just need to let this dry a little more and then I can start basing it. It's going to be nice!