I used the reference photo as a clone source for the color, selected a rough, oil brush (Jeremy’s MishMash from Jeremy Sutton’s Painter X Creativity Book) and set it’s opacity to 80%. I liked the effect it gave for the mountains. I set the transparency for the tracing paper to about 60% so I had a guide. All in all I like the effect it gave me for the mountains.
That effect didn’t work so well for the C-17 shape. For that I selected the Den’s Oil brush. I had a smoother look & feel and fit better with the texture of the aircraft.