Rocks on the Right: Place darks first, on Right side (shadow side.) with a flat brush (Thalo Blue+BU). Use flat strokes in all directions. Highlight on Left side with White + YO, & using same flat strokes to make angles on rocks. Blend between lights & darks with dry-wiped flat brush (very lightly).
Rocks on Left side: Dark side is on the Left (TB+BU+tch Wht). Highlight w/White+Dark mix + more TB