What is it?

I can almost always gauge someone’s Photoshop skill level by the way they change their Brush size. This created two neat categories.
Beginner Photoshop Users use the Brush Preset Picker to select a brush, hover their mouse over the image to gauge brush size then return to the Brush Preset Picker to adjust the brush size and so on.
Advanced Users use the bracket keys ([,]) to change the brush size or add the Shift key to the mix to change the Brush Hardness.

Photoshop CS4 adds a new method of adjusting brush size breaking my two easy classifications. The Drag-Resizing Cursors which allow you to click and drag on your image to resize your brush using a special keyboard shortcut. In Photoshop CS4, with the brush tool selected, hold the Control/Option keys (Mac) or Right-click+Alt (Win) while clicking and dragging the mouse. Move the mouse down for a larger brush and up for a smaller brush. A red overlay will temporarily appear to show the size and hardness of the brush.

Why is it important?

The two classifications of Photoshop users aren’t meant to be pejorative. Instead, they’re based on practical experience. People who use Photoshop (or any application for that matter) gravitate toward the fastest, and most efficient way to work. In order to perform their work effectively, and not get bogged down in the maze of pull-down menus, dialog boxes and options, master users let their fingers do the walking, fluidly jumping back and forth between tools, changing brush sizes and generally working their magic on images without breaking rhythm.

If you want to work more efficiently, try learning the keyboard shortcuts for the tasks you perform every day. It will take a little while to memorize them, but after a short period, you’ll find yourself forgetting to remember, your fingers select the correct tool automatically without thought or attention.

Welcome to the Master-level. I’m glad you could join us.

Bonus Tip: To get into the Ninja-level, use the following keyboard shortcuts to drag-resize brush hardness. Control/Option/Command while clicking and dragging on the Mac or Shift/Right-click/Alt on Windows.