Woking on mid-range rock shapes

Tonight I worked on mid-range rock shapes and values. I tried a couple of brushes to work on the part; 25mm(1") longer/thinner/softer flat brush, Utrecht 209 series #10(1") and #8 brushes. I ended up using the #8 for its firmness in soft feeling and not too broad to be able to define some sharp edges at the same time to cover planes.