Next I painted up the armor. First I went over a few key areas with a Tamiya weathering pen, I used mud of course, but I didn't apply it directly to the armor, I rubbed a little onto my thumb and then rubbed my thumb onto the armor where I wanted that red/orang color to be. Then I went into the real paint work. I mostly used gray, brown, and barely a touch of green. I laid down multiple layers, wet, then dabbed with a paper towel. After each layer was dry, I used a dry wirey scrubbing sponge and lightly scrubbed over the dry paint.
Next I wanted to add some clumpy, textured mud to a few places. I used some of the earth/terrain you can buy for model train sets, and mixed it onto my paint with some matte medium for some areas, and gloss medium for other areas. I applied it to the places that made the most sense to me, keeping in mind how the Trooper might move, and how gravity would affect the mud. Once it was dry I wiped the whole figure down with a cloth to get any loose "mud" off the figure, so the look wasn't overwhelming.
I went over everything and added some scratches and chipped mud etc. The last thing I did after assembling the sniper plate and attaching it to the helmet, was to flick some gloss paint to add a sort of rain effect.