Figure 3 from: Coleman ChO (2018) Shadings in digital taxonomic drawings. Zoosystematics and Evolution 94(2): 529-533. https://doi.org/10.3897/zse.94.28624

Figure 3 A) In Photoshop select newly created layer and apply shading by spraying pixels onto selected areas. B) After airbrushing, make first layer, containing the outlines, invisible by clicking on eye icon in "Layers". By this only the pixel clouds are retained.