>>5822587Everything - shoulder, elbow, wrist, and fingers. You naturally use all of these depending on the size of the drawing/mark. People who tell you to use shoulder only are typically physical media painters who work standing up on a vertical canvas, and even then they still have wrist-based "flicking and dappling" strokes for detailing.
If you're worried about carpel tunnel, then you should focus on is relaxing your grip. Most people hold their pens way too hard.
If you're using a stylus, you also want to limit the amount of times you use the buttons on the stylus. If it's unavoidable, you can periodically roll the stylus, switching button presses between your thumb and your index finger so that neither one is overworked.
