RobM – In regards to your inquiry on faces. Now, my experience is more with women’s faces, which I usually do smooth, so my technique may not help at all with men’s faces. I normally use a dark color for the face and then put a light colored gradient on top as my base. It creates more of a 3-D effect by making the face appear to round towards the edges. The rest of the zypping, IMHO, is a matter of what expression or effect you’re trying to convey. I nearly always apply some zypping near the eyes and nose. Also, zyppng the lips really makes them stand out.
AMS – as always, you do an awesome job with the look of your characters.