Here’s an example of how hand controls that wrap around the geometry can be used for a collision shape as-is.
With more points, it’s possible to achieve greater accuracy, and her nails get somewhat sharp which has a stronger effect on friction than you might want. Normally the nail would perhaps bend a little?
See those little green pies, and orthogonal red lines sticking out from her knuckes? Those are her limits, they only permit rotation along one axis - X - and only within some range - the surface area of that green pie.
Here’s what it would look like without limits.