I've recently started learning to spin poi (it's not important; you may think about dancing) and found that my left hand requires a great deal more attention to follow the trajectory I have in mind than my right one. This is extremely pronounced before I form some muscle memory, and becomes somewhat less severe after. Obviously, the only way to get better is a lot of practice, and that's what I intend to do. However, while thinking about this problem I visited quite a few websites with the advice on how to improve the coordination of non-dominant hand. Some of them recommended writing by that hand. I doubt that developing fine motor skills will help me with the complex hand movements heavily involving elbow and shoulder. So I decided to ask for a reference, preferably to some scientific paper (this hypothesis looks easily testable, so such papers probably do exist). I was unable to find anything on this topic, but maybe you could give at least a personal story.