That's what you can do with this, it's the same thing except you would need to move the finger dials instead of the the head bend dial.

Best way to think of it is to clear your mind of anything you assume it does, and just visualise that a dial will copy whatever dial edits you make to any other dials between the Start and Stop Teaching presses.  A finger, a head, a foot, or even ten things at once, it still works the same way.

Even the bend of one part of a finger or the whole finger (which is what you want).

I just tested what I wrote above, it works fine so all you have to do is ignore the head bend part and do your single finger dial edits instead.  It's exactly the same thing.  If it doesn't work for you I'm pretty sure it's because you're not moving your finger dials before you move the dial in the window.

All you have to do is make sure Poser sees you touch the dial you intend to edit before you move the dial in the window.

It's a shame I can't explain it better, but what I'm telling you is what you need to do to make a custom finger grasp.  If you don't do it this way you have to do it old-school and that's a lot harder because it means doing it in a text editor as ockham pointed out above.

I'd make you a quick vid but I have no way to record it.