When I drew them, I was looking for a finger hierarchy, picking a focal finger to push the "pose" a bit. That's usually the pointer, thumb or pinky. The 2 mid fingers tend to act together as supporting players.
Proof that practice helps: I drew the hands on the second sheet first. You may notice they look simpler, not as well drawn. By the time I got to the top sheet above, I was warmed up.
Drawn with willow charcoal and Wolff's 4B carbon pencil on smooth newsprint (18x24").