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%.