You've already used the Brush tool for all kinds of things in previous chapters: editing layer masks (Using Layer Masks), creating a selection (Using Quick Mask Mode), colorizing grayscale images (Colorizing Images), and so on. In this section you'll learn how to paint with it, and in CS5 it's a more realistic experience than ever before. But first you need to understand a bit more about how this tool works. Grab the Brush tool by pressing B or by clicking its icon in the Tools panel (see Figure 12-11).

Figure 12-11. The Brush toolset also harbors the Pencil tool (see the caption of Figure 12-17 on page 508 for more about the Pencil tool) and the Color Replacement tool (page 454). Just press Shift-B repeatedly to cycle through the tools. Use the Options bar to set your brush size, choose the kind of tip you want, and adjust opacity, among other things.