The brush tips determine the shape and properties of the brush check your tool box for the parameters.

You can change the shape, the opacity, the size, its hardness and its density. With a tablet that has a pressure sensor you can use that to vary the pressure.

When I use Paint Shop I like to use the Show Brush Outline option on the second page of the tool box. I prefer my brushes to have 100% opacity, but to transform a gradual shade you will want to vary that, changing the density will give you a pattern like not all of your brush hairs are touching the paper. A hard brush will have a uniform opacity from center to edge, but you can reduce the hardness to give yourself an undefined edge. If you paint with a brush that doesn't have 100% opacity then you can use the Build Up Option to add other colors or to increase the color in some areas and not others.

Remember that other tools like the clone brush will use brush dimensions and have the same effects. The Special Tool, usually denoted by a hand, will let you access soften, blur and a dozen other effects. You can also vary the brush with these. I use the smooth option to make skin tones smoother and to get rid of pixilization at the edges.

You can also draw and paint with the paint brush and if you press the little paint brush icon in the tool box you can get charcoal, chalk, marker and other effects.