Go and grab the .blend file here

Once I chose a pose to polish I applied all armature modifiers as shapekeys and started adding more shapekeys on top. Since the rig was very simple and the weighting was mostly automated there were many areas that were twisted and morphed in weird ways and lost or gained lot's of volume. In terms of the shapekeys there was generally one "Armature" shape that defined the overall limb rotations (I also further defined this shapekey for the hand poses), 1-2 "Adjustments" shapes to fix broken areas and sculpt more detailed deformations onto the model, and 1-3 expression shapes to sculpt the expression & additional exaggerated variations just like I did in the Expression Tests.