The green stuff weathered (3d step, my '"drybrush'")

Okay, as you can see from the picture, I used only 3 colours for this, I blend them, and I apply them as a not much diluted screen on the parts that would normally stand out as highlights if being drybrushed. That's it in fact, i never do any real drybrush on my models because the effect is too hard and visually quite crap.