Acrylic Paste...this stuff is so cool!

I love this stuff! 

It's a sticky paste a bit like gesso that you can use to fill, texture and even undercoat with. I get mine when on holiday in France in the local supermarket of all places. It's brilliant for coating laser cut buildings and is designed as a preparation for artist's canvas so takes paint very well, preventing the sponge effect that you often get with mdf surfaces. 

As you can see, I've covered the hill tower with a couple of layers of the stuff then stippled it to create a textured surface, although in the past I've just smoothed it over with a wet finger when it's half dry to give a plastered adobe effect. You can also sand it back to smooth off the texturing and provide a key for painting. It's not expensive either, at least in French supermarkets, with a big tube costing only a few Euros.

I've not quite managed to hide the ubiquitous laser cut kit joints but will go back and fill them before I overspray the whole lot with a Halfords Ultra Matt Khaki undercoat. I'm going to add a hatch to the roof, so that there is access, and some rubble around the base to show where the parapet has fallen down. I'm quite pleased with this scratch build so far and quite fancy making another one, this time in the form of a tall, thin lookout tower.