Aging affects the face in far more fundamental ways than just superficial wrinkles. In this video, Sculptor Philippe Faraut makes the changes in soft clay to represent the journey of a typical male face from youth to old age.
When drawing older faces, American illustrator Andrew Loomis advises eliminating surface wrinkles and stating only the main lines and forms: "The impression of age is maintained without the incidental and insignificant wrinkles."
Book: Andrew Loomis, Drawing the Head and HandsThe artist's website, with more info on his materials and tools
Mr. Faraut's books:
Mastering Portraiture- Advanced Analyses of the Face Sculpted in Clay
Portrait Sculpting: Anatomy and Expressions in Clay
Mr. Faraut's DVD: Techniques of Sculpture: Geometry in the Clay Portrait