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 give you a percentage of undo, lightening your stroke. You can also use the pop-up Mode menu to alter how your stroke blends with the object below it.