Could Cannabidiol steady a hand?
I think this is a fantastic question.

As far as the Parkinson's application, it's definitely within the realm of possible. Taken form a recent review:


  Preclinical research in animal models of several movement disorders
  have shown variable evidence for symptomatic benefits but more
  consistently suggest potential neuroprotective effects in several
  animal models of Parkinson’s (PD) and Huntington’s disease (HD).
  Clinical observations and clinical trials of cannabinoid-based
  therapies suggests a possible benefit of cannabinoids for tics and
  probably no benefit for tremor in multiple sclerosis or dyskinesias or
  motor symptoms in PD.


Kluger et al. in Movement Disorder, 2015 (The Therapeutic Potential of Cannabinoids for Movement
Disorders)

As far as every-day hand steadiness, I haven't been able to find any good sources yet. I'll keep reading, and update this if I find anything interesting.