1: Simply crumble the soft plastic film to add   more 3-D contour.

2: Tack the material to your framework either with low-temp hot glue or staple gun.

(Avoid using liquid nails or some glues as they will dissolve the plastic.)

3: Blend seams with Flex-Paste (WD1205) or Gypsolite (EX0050). 

4: Apply a flat, dark base coat color wash. Use only Acrylic or Flat Latex paints diluted and mixed with a little rubbing alcohol for all weathering.

5: Sponge on additional mid-tone color giving the rock a 'stipple look'.

6. Brush on light color highlights for out cropping textures