Hi @manuelhooks, thank you very much fo your participation!

The drawing of a hand performing an activity adds interest to it as well as makes work easier since many parts are hidden from view, as in this case.
Without a model as a reference, the mistake is made of drawing characteristics that do not exist or of placing them erroneously, as is the case of the shadow on the upper part of the hand but not on the thumb, nor on the pencil. What you call shadow effects are just dark spots.
One of the great qualities of drawing is the possibility to learn from the model we are trying to interpret.
Try to use a model the next time you draw.