Yeah, I fully agree with you on “continuously growing” and definitely plan to do that.
I will film her with a green screen and remove the background so that should be easier.
Track matte will probably make it but again I’ll have to go frame by frame to make sure it follows her finger.
I remembered seeing someone who was using the pen tool to draw a line and something would then follow that line. Do you think this technique could make it to do what I want and if yes, any TIPs on how to do it?