Brushes used in watercolor are usually made of soft hair, although bristle brushes are occasionally employed by some painters. Pure red sable brushes are universally considered the best since they are soft, resilient, and have excellent points. Well-made red sable brushes are very expensive, but substitutes, such as "camel hair" (really squirrel and other hair) brushes, exhibit noticeable differences which make them harder to control. Usually three first-rate brushes--small (no. 3 or no. 4), medium (no. 7 or no. 8) and large (no. 12)--will serve the artist better than will a dozen cheap brushes. A flat soft hair brush, about 1-inch wide, is a useful addition to the three round sables. Fine sable brushes may be purchased in quill mounts without wooden handles, as well as in metal ferrules which are attached to handles. After use, brushes should be washed in mild soap and water and then thoroughly rinsed in clear water. Between painting sessions the brushes should be stored and carried carefully so that their hair does not get bend out of shape. Art supply dealers sell brush boxes that have holders to keep the brushes in good shape as they dry. Brushes made of sable and other soft hair may be damaged by moths. Mothballs or moth flakes, such as are used to protect clothing, can be put in the drawer or box in which the brushes are stored to prevent moths from spoiling the hair.
Artists should never shape the tips of their watercolor brushes by drawing them between their lips, because of the danger of ingesting pigment that may be poisonous.
Tube watercolors are customarily used with a metal palette that has small depressions into which the moist color is squeezed from the tube. Such palettes also have large sections in which washes may be mixed.
It is convenient to have two containers for water: one in which the brush may be rinsed; the other for clear water to dilute the colors. For outdoor work and traveling, unbreakable plastic bottles made of polyethylene are convenient. A sponge is useful to moisten paper and to remove color. [pp. 132-133]
[Kay, Reed. The Painter's Guide to Studio Methods and Materials. Englewood Cliffs, NJ: Prentice-Hall, Inc., 1983.]