Like the buttons and dials in your car, keyboard shortcuts are the "user interface" with which you control Photoshop. Have you customized these commands yet? The whole point of keyboard shortcuts is to save you time and avoid wasting energy. With this in mind, it's worth considering your personal needs when working with keyboard shortcuts. In general, shortcut keys are designed for easy recall: ctrl+s = save, etc. In this video I suggest that a better scheme for assigning keys is based on the position of your left hand. Re-mapping the keyboard shortcuts with this new prioritization will reduce your hand strain and speed up your painting technique.