Well time for more, added the roof to the staircase tower, finally. Just plain paper grey Canson MIteintes coated with a couple of thin coats dark grey acrylic primer with the airbrush. Made a small mistake and added Ammo African dust to all the seams tossing the bottle. One complete mess. Toss the lid they already warned me often..big luck for me I work on a big A2 sketchbook, so only the paper soaked. Back to business, added this nature effect to all the seams and feathered it with odourless thinner. After that I went through my pigment collection and picked a few, Europe Dust, Industrial City Dirt, Factory Grey and Dark Mud all from Mig Productions. Placed, feathered, moved finally touched down with odourless thinner blown dry with just the air from the airbrush. That’s where the double action comes in handy. On the sloped roof I painted a couple of streaking effects before I went over with pigments. Pigments also had a light streaking motion. Finally I speckles on some dark earth tone wash and a light dust wash wich I feathered with a damp brush and gave a streaking motion on the sloped roof.