Ok. so I'm helping a friend with some rendering techniques, and I'm breaking it down as I go, so I figured I'd throw what I'm doing up here. Make of it what you will!
#1 This is just a flat gradation from dark to light.
#2 This is a horizontal line drawn over it for a more textured effect.
#3 This is how I block in shapes to create a textured wall. I put some thicker lines on the top of the shapes to make them visually recess. It gives it the look of shadowing. Really, this could be left like this. I just like all the little lines!!
#4 This is the same technique from #1 inside the shapes, outside the shapes is the same technique, but higher on the value scale.
#5 I wanted to isolate the little ridge of rendering that I use to create some dimension. #6, and the line at the bottom further break down the process.
Give it a try!!
I've got more up my sleeve, and it's fun to break down this stuff. Stay tuned.