Having created the basis of our plaster bunker in part one, it's time to add some details. Note that this is best done within an hour or two of casting i.e. while the plaster is still damp and relatively soft.
We'll begin by carving some firing slits. The best tool for the job is a craft knife with a chisel blade however you could probably do a decent job with a relatively sharp flat bladed screwdriver. The technique is to use a straight edge and drag the tool repeatedly on the surface of the plaster to make a shallow channel. To further increase its depth, use the tool as a chisel, diagonally cutting slices of plaster. It'll get deeper pretty fast but don't rush it. Cutting the plaster out in smaller pieces will result in smoother edges. Also bear in mind that there is little no point in going all the way through to the hollow; a deep channel is sufficient.
Now for a door. This is simply marked out and then chiselled and cut out using the craft knife (with chisel blade) and a serrated kitchen knife:
Battle damage is created using a sharp pin or the tip of a knife. Start with a hole at the centre of the impact, make lines radiating outwards and finish with concentric circles. The damage illustrated below is suppose to be from heavy mortar fire. Actually, I have no idea how it is supposed to look like, but this effect has worked for me.
That brings us to the end of the plaster carving and the piece should now be left to dry out. Spending the night in an over on it's lowest heat setting will do the trick. After this, other details can be added prior to painting as you will see in part 3.