I wasn't going to do any more on the layout today, but I stumbled across the tester pots of paint that I bought a couple months ago. So I decided to bite the bullet and try them out on the layout. I have to say, despite only having used the big brush that comes with the pots, the effect seems to be perfect for what I had in mind. It will of course need going over with a finer brush, but it seems like a great first step as base colours.
It really has transformed this board a great deal, just as I hoped it would!