Also for washes, mops are thick, round brushes, either pointed or oval in shape, that create large, organic forms. When applied with varying angles and pressures, they can be used to create a wash of color that subtly changes from broad to narrow.
While it’s possible to increase the range of marks that a brush can make by experimenting with the way it’s used—for example, you can play with using the brush’s edges, pushing paint rather than pulling it, and vary the amount of paint you’re using—there’s no substitute for learning about the inherent strengths and limitations of each brush shape. With this knowledge, artists can determine the marks and paint consistency that they prefer to use, and the brush choices will be obvious.