GET MORE CONTROL OVER YOUR PAINT STROKES

Photoshop lets you affect a brush stroke even after you've painted it by using Photoshop's Fade command (found under the Edit menu). Fade works like "undo on a slider," and dragging the Opacity slider all the way to the left will completely undo your freshly painted brush stroke, but if you stop anywhere before the far-left side, it will instead simply lighten the stroke. You can also use the Mode pop-up menu to alter how your stroke blends with the object below it.