if i was doing this i would…
use the write on tool to reveal the image as it was being drawn ( though you may need to split up the paint layer a bit more and do it in seqence)
Make one comp for each part of the drawing (ie outer triangle, inner triangle etc) on each put the hand layer on the comp as well ensuring that the anchor point is at the tip of the brush. (paste the hand layer from the 1st comp onto the different ones to make sure the anchor point remains in the same place)
Twirl down the expressions for position on the hand and pickwhip to the write-on position
assemble all the comps together in a final comp adding additional animated “hands” where needed to join all the comps up….
DONE
Dunno if this is the best way to do it but its how i would start out.
Hope this helps
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Video Producer / Motion graphics designer https://bexmedia.net