The basic rule of thumb for mass and shape is, the bulkier and wider the shape; it will appear more masculine. And the longer, leaner, slender the shape; it will appear more feminine.
Different pose will give masculine/feminine quality. So when I want to make my hand appear more masculine, I think of stereotype of strong big person, like a superhero (hulk, superman, Xena … etc), or Michelangelo’s hand from creation of Adam. And when I’m designing feminine hand, I think of a graceful dancer. Another feminine stereotype pose is having the pinky flares out, like the way English ladies holding their tea cups.