Is there any simple way I can shade a drawing with the brush tool?

Hi, I am using Toon Boom Harmony Advanced at the moment and I would like to know if there is any simplistic way I can shade a drawing. For example, let’s say I drew a simple stick figure with hair. What if I wanted to paint some shadows under the strands of hair. Is there any like magic wand tool or something in the program, or anything close to it? another example is that if I drew a circle and painted the inside of it, lets say, green, is there a way I can somehow shade the bottom of that circle a slightly darker shade of green without getting the lines all over the outline of the circle? I’ve looked up how I can do this, but didn’t find a lot of results I wanted. Thanks

Duplicate the hair-Layer, drag it behind the hair layer, move it slightly down,
repaint in black or else, apply a gaussian-blur, done.

Apply a gradient and edit it to your liking.