Using rouge you can highlight the 'sunken' part of the skin a bit more.
Work on a dry base, so on skin that has been powdered off. Use the Powder-Rouge Brush to take out Grimas Eyeshadow/Rouge in the desired colour. Put the powder brush vertically and tap with the hand to disperse the powder in the hairs so the powder does not just end up on the tips of the hairs. Smooth the colour out with the flat side of the brush, so do not dab it on.
For a natural effect, you can apply the rouge to the cheekbones, the temples and under the eyebrows, and light touches to the neck.