Exploring shading using watercolor paints and the ipad.
Using the Procreate app for the ipad I created this circular blotch of colors. The app has many choices of brush styles, includes a layers panel and the popular smudge tool. Best thing about it is that after few hours of smudging, your fingers come out totally clean!
Light & Shade Resource
Here's a 10 page overview to lighting and shading with great visuals: Famous Artist Cartoon Course – Light & Shade