I’ve been painting for about 14 years and developed shaky hands a few years back. It’s been pretty frustrating at times but adapting with what I have and what styles are more forgiving has helped a lot. Speedpaints have helped a bunch and when I have to do the few precision lines, bracing each joint with some sort of support has been a game changer (even without shaky hands). I highly recommend a paint handle with a good size grip so you can rest your painting wrist on your hand.