Using watercolor successfully is all about controlling the flow of pigment on the paper. The looser the painting, the more water is used. Pigment goes where water flows. Watercolor lends itself to diffused shapes.
There are 4 ways to apply pigment/control paint. In these descriptions, the first word refers to the moisture content of the brush, the second the moisture content of the paper.
1. Dry on dry
2. Wet on dry
3. Dry on wet
4. Wet on wet
Dry on dry. A brush with little moisture is used to spread pigment on dry paper. This technique produces a rough texture that stays in one place. Also called rough brush or dry brush.
Wet on dry. A wet brush is used to spread pigment on dry paper. The pigment stays put but you can vary the value of the paint winthin the brush stroke by varying the amount of water used.
Dry on wet. A dry brush loaded with paint is used to spread pigment on wet paper. The pigment can be moved around and diffuse shapes are produced. This method allows control of shapes and produces soft edges. Many watercolor painters use this method the most.
Wet on wet. A wet brush loaded with paint is used to spread pigment on wet paper. The pigment can be moved around and the result is soft diffusions with no control of shapes. This is my favorite technique and provides the most surprizes!