Yah, when I say wash, I just mean wattered down paint. I didn't use GW colours, but here's a picture of the colours I used.
The two GW colours at the bottom are scorched brown, then bestial brown. (from left to right) I didn't use these, they are for reference only.
I undercoated with one of the browns on the left, for the life of me I can't remember if it was the redder and slightly darker one or not, sorry!(It was only yesterday that I painted it too!
) I mixed one of those brown with a bit of black to make it darker, then mixed it about 50:50 with water, maybe a bit more water. Then I applied the brown. Once this was dry I drybrushed with the tan colour in the middle. (It's almost the same colour as bleached bone, but not quite. BB has more of a greeny hue, whereas this one is a little warmer and redder.) After that I did a light drybrush of the grey colour on the edges of the boards where they were broken. (GW probably have a comparable grey, this one is slightly blue-ish, and I've heard that some of GW's are to. Maybe try fortress grey?) Then I did a very very light drybrush of the ivory colour over everything, to tie it all together. At least that's what I'd like to think, I'm not sure if I actually got any colour onto the wood from the last drybrush, it was that light.
I hope that helps, sorry about not using GW paints. I just started out with the craft paint that my mom had, and have now slowly added some GW paint as needed, but I still use the cheap craft stuff for terrain, no use in using the expensive GW stuff.
Oh, and as a last note, I wash the wood with the initial dark brown rather than just painting it, so the natural grain and texture can come through. The brown will also soak into some parts of the wood more, and some less, giving it a slightly different colouring, which I like. Once you put the drybrushes over it it really helps to tie it all together, even if it looked a little wierd before. You might be able to tell that one of my boards soaked up a lot more than the others. One of the two middle ones.