Keyboard shortcuts for brushes include the bracket keys for cycling through all available brushes. The illustration on the left below is the options menu found if you click the arrow in the upper right corner of the brushes pop-up palette. The pop-up palette is found by clicking the down arrow next to the brushes thumbnail on the options bar. On the right below is the dialog box you find if you choose New Brush from the options menu. You can create, preview, and save your own brushes here.
Diameter sets the brush's size.
Hardness affects the fuzziness of the brush's edges. Spacing determines how often an imprint of the brush's tip is applied. Spacing can be set to give a dotted line, or one where the brush dots barely overlap, like a beaded necklace. To paint without spacing, deselect this option by unchecking the Spacing check box. This spacing gives a smooth, continuous stroke.