I prefer to do this before working on the lips, as the majority of these lines will connect into them at some point, and it’s easier to have the groundwork done ahead of time. To start, I finally follow through with many of the edges, once pipes, created to shape the nose and eyes.
The edges are then connects up and over the chin, allowing me to shape it, rather than at the edge of the chin and down the neck line. A loop is also added behind the jaw, to create that recession below the ear without drastically adding to the polycount. It also loops under the chin, allowing me the verts to shape the jawline and nook between the adam’s apple and upper neck.
Finally, some verts are pushed and pulled to shape out the neck and shoulder. At this point, all the necessary edges and verts have already been created just from working on the stuff that came before it.
From Gray 