Map channel 3 - Symbols
Again, when preparing this mask, I made sure I kept enough "black empty space" between the symbols. That is also why for this map I turned tiling off - to have more empty space to work with on the corners.
So now we go again through every armour part, add another unwrap modifier and set it to channel 3. First step is to select all the UV's, scale them down and take them outside of the UV box (which should be enough to "make a clean start" since the tiling is turned off). The idea now is to select the polygons that will have a symbol, hit planner and manipulate the UV's until you are happy with how the symbol sits on the model. Again, immediate viewport feedback makes it possible to nicely "deform" the original shape of your symbol to fit the shape of your models more "naturally", this also helps avoiding having a cloned look when using the same shape several times. (Take a look, for example, at how much the big shape on the helmet is deformed from its original texture to fit the flow of the helmet) (Fig.21).
Map channel 4 - scratches
I added this one later, but since the scratches should also appear on the side decorations and symbols, I've added this mix level below them (like I've mentioned earlier, the order of the mix levels in the material is important and it wouldn't make sense to have the scratches on the armour stop where there are symbols and side decorations).
For most of the armour's parts I've simply placed an UVWmap modifier with map channel 4 and did a quick move/rotate/scale tweak to the gizmo to determine how the scratches fall (Fig.22 & Fig.23).
In Fig.24 you can see the final image.