Quickly Change the Size of My Brush?

With the Adjustment Brush selected, Right-click on your image, and then drag to the right to make your brush bigger or to the left to make it smaller. You’ll totally dig this visual way of resizing, but if for some reason you don’t, you can always jump to the next smaller or larger default brush size by using the Left and Right Bracket keys on your keyboard (they’re located to the right of the letter P). If you’re charging by the hour, you can also do it the long way by scrolling to the bottom of the Adjustment Brush panel and moving the Size slider manually.