Construction
Base
Cut an irregular piece of thin card, slightly larger than the bunker.
Walls
These are made from foamcard, with angled buttresses, also cut from
small pieces of foamcard. Make sure you use a sharp scalpel blade or
it will rip the foam filling and you won't get a flat edge. The back
wall can be left open, so that a base of figures can slide inside. Remember
to cut the slot at the front from the foamcard before you glue it all
together. All these parts are glued together with PVA woodglue.
Roof
The roof is a small piece of mounting board, the top edges of which
can be chamfered with a sharp blade.
Filler/Tile Adhesive
You will now need to use some filler to plug any gaps and to make the
cut edges of the foamcard flat. The filler will also give it more of
a concrete-like texture.
Basing
Now apply your standard basing technique.
Painting
1) First base coat the whole building with a mid tone such as grey
or this muted brown: 
2) Next wash it with a very dark brown. 
3) Now drybrush with the base coat again.
4) Finally apply a highlight drybrush.
