Wow, ok I hate to say this, I really don't think this is a job for PaintFX, but rather SplineIK.

PaintFX will just keep flipping around in a jerky manner on you if you move the curves too much, or twist them back over themselves too much.

For the specific type of shot your going for, you might be better off modeling a long "branch" with bumps and small branches, bark and dirt textures etc. then check the help on how to hook up a splineIK rig to it.

I've never done it myself, but I've seen character riggers at my job do it, and they get great results in a short amount of time.

So, instead of going for a "hand", you might want to think of it as creating a few "tentacles".

Lemm know if that helps you or not