Do a trial on a half face first, before you start on the whole character. Apply your base colour, put a bit of shadow on one cheekbone below, and a lighter shade above it. On the other cheek leave things alone. Now look at your face from straight on, and from a 3/4 angle. Just that simple difference can make one cheek appear to have more definition, to stick out more, or to be thinner. That’s basically what theatrical contour does; highlights draw things “forward”, shadows push things “back”.
The same principle applies to the nose, the forehead, the jawline, the eyebrows, the eyes. A shadow by the nose makes its centre seem more pronounced, and a highlight on the nose enhances it. A shadow on the bottom of the jaw separates the face from the neck. Highlights on some sections of the forehead and the cheekbones make the different planes stand out differently in the light. All this is very dependent on placement, so you’re better off examining your own bone structure and where shadows fall on it, rather than trying to copy the facial markings of another person.
A difficulty at the beginning is that contour can look too much like drawing. It’s true that a dark band under the cheekbone will do the trick, but it will also look completely unconnected to the rest of the face. Instead, cream makeup should be applied thinly, and the edges blurred with a brush or sponge. You can have a strong centre to your shadow, with the outside edge fading away. This way the shape remains, but it doesn’t appear as a flat painted-on line.
The distance of the audience plays a role in how much of all this remains visible. Once you’ve applied your first layer, step away from the mirror or take a picture from a few metres away. Look for the overall shape, not the finer points of blending. Does the cheek still look raised? Does the jaw still look more pronounced? Can you see the difference between the highlight and the shadow? If the effect has gone, add more pigment. If the shadow takes over the whole face, reduce it before going on.
It’s also good to move your face while you’re working. Smile, raise your eyebrows, turn to the side, and return to neutral. Seeing your face in natural expression will help you see where the skin creases and where shadows normally lie. This is particularly important when working around the eyes, mouth, and forehead. A character can accentuate these features, but they’ll usually read better if they stem from actual facial expression rather than from ignoring it.
There are many different ways to apply the same highlight and shadow to a character. Stronger shadows over the brows will make the eyes seem more sunken, more highlight on the cheekbone will give the upper part of the face more definition, additional shadow on the bottom of the cheeks will make the face look thinner and sharper, while more subtle contours will give a less stark impression. The point isn’t to adhere to a rigid pattern, but to understand what a given placement does, and be able to make choices based on that.
When you finish, examine your face from straight on, from the left and right, and from a greater distance. Pay attention to which changes in the facial structure still stand out, and which vanish outside of the close-up mirror view. The latter is helpful, because it tells you what you need to strengthen, adjust in position, or blend more cleanly, next time.