Tunnel Liner Sides
Here a close up shows the texture and paint on the sides of the tunnel liner. I mixed up some of the small bottle paints and dry brushed onto the surface making sure to use some random coloring like you see in real life. Finally I used some ground caulks (top) to do a little weathering.
I am trying to get something close to rock shapes and construction you'd see in a tunnel. But I'm also trying to do something that will just pass when pictures are taken. Remember...most of this will only see light from an engine when passing through.