I’d aim to get the major forms in first, then retopologize for a better sculpting base for the final details. With that in mind, the hands and head can be treated as separate subtools for now. The hand could be a simple case of sculpting just one, duplicate it symmetrically (mirror and weld, subtool master, or just duplicate the subtool and use the mirror deform), and then transpose the new arm into it’s proper pose/position.
For the head, start out with a base mesh (new subtool too) that is completely symmetrical as far as the topology goes. Then you can transpose it into the place/angle you need it, and enable Transform: Use Posable Symmetry