It is a simple structure. The yellow effectors are positioned and created to start making a finger control.
The arm chain is a simple 2 bone placement with an Up Vector to a null to control the elbow.
I also am using soft effectors on the arm, and you could possibly use Stretchy soft effectors too (an addon)
Download Soft Effectors
Just make sure your chain with the effector is on Default mode (not 2D nor 3D)
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I link rotation nulls to the bone nulls why? So I can animate the bone nulls independant from the parameter box when needed. But if I want a curl, the orientation nulls that the bone nulls are constrained to would be used with cascading expressions to then get a curl via a slider.
An example panel below:
But you shouldn't need that for this case. I'll explain this later, using GEAR.