Nick McGavern demonstrates how to take existing geometry in ZBrush and edit the topology so the model is better suited for production needs.

This is a short demo showing how to take existing geometry and to edit the geometry/topology to better suit your mesh needs.
Load a Zsphere. Tips -Hovering over the verts will turn your brush green, you can then click on that vert to use as a starting point.
To reset the beginning point of your vert placement, double click in space, otherwise it will start at the center of your zsphere.
Make your draw size about 1-3 so you are only effecting one vert at a time. This method can also be used to merge two tools, once they have been merged down to one. Also great way to add geometry to a sculpture without having to venture out to another program.