Copy a Shape Layer's Path to a Still Layer's Path

I'm using Trim Paths on a shape layer to animate the "drawing" of the shape. Then I have a still image (my hand) that I want to track the drawing of the shape layer.

In AE, I do this today by setting the trim paths, then copy the Shape Layer's Path.  I go to the still layer, select the position attribute and paste. This gives is the still layer key frames which match up with the shape's animation.

I was thinking I could loop through something on the shape layer and then create the keyframes on the still layer. However, I'm not sure what makes sense?  Should I use valueAtTime() on the shape layer's path?

Any ideas how I can I replicate this workflow in ExtendScript?