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It is very helpful to put up a chart outlining basic makeup in the dressing room(s):
Specialty Makeup
Age
Have the actor scrunch up their face, and use an angled brush and a foundation a few shades darker than their skin tone to line the places that their face naturally folds (especially on the forehead, between the eyebrows, under the eyes, around the nose and mouth, and on the chin). Line on top of those lines with white or a pale shade, then blend. For greying hair, use Ben Nye Hair White/Grey or similar.
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