You'll find that a waterbrush can be used to create a flat wash in the same was as a normal watercolor brush (Photo 2). Simply dip the brush in and out of the paint as usual. You'll find that the moisture in the waterbrush doesn't make a difference, provided you don't squeeze the water reservoir and provided you pick up fresh paint with the brush regularly.
It's when you're wanting to paint a graded wash (Photo 3) that the uniqueness of a waterbrush makes a huge difference. You start by picking up some paint and laying this down, then simply continue painting without adding fresh paint or clean water, or rinsing the brush. The water in the waterbrush gets added to the paint as you're working, gradually lightening the color to create a graded wash.
Be careful that you don't squeeze the water reservoir and end up with a puddle of water on your paint (Photo 4).
