Change the Hardness of a brush on the fly
You probably know that when the Brush tool (B) is selected, you can decrease or increase the brush size by pressing the Left Bracket ([) or Right Bracket (]) key, respectively. But at times it’s useful to change the brush’s Hardness setting as well. To do this, just press Shift-[ (the Left Brace {) to reduce the hardness by 25% or press Shift-] (the Right Brace }) to increase it by 25%.