Makeup combined with CGI

Figure 1: Den of Geek (2009) 

A common use of makeup in film is to age a character. The Curious Case of Benjamin Button takes this to the extreme. Not only does the age of the main character change throughout the film, but he ages backwards. On top of this, all of the various stages of age are portrayed by different actors, but they all had to be recognizable as the same person. To solve this problem, the filmmakers used a technique of imposing one actor’s face on top of another’s body. Brad Pitt plays the main character. For some sequences, Pitt could play the character directly with the help of makeup and hair styling, but for others his facial features had to be replicated on another actor’s body (the filmmakers have said that 52 minutes of the 166 minute film don’t feature any direct footage of Brad Pitt). 

Figure 2: FX Guide (2009) 
This was most obvious at the beginning and end of the film. At the beginning of the film, the character is a baby who looks aged. For these sequences, the studio took digital images of Pitt’s head and aged them with the computer, rather than taking a digital image of Brad Pitt in makeup to look aged. Still, the expressions of the character during those sequences are modeled exactly after Pitt’s performance. To make sure all of the actors who portrayed the various stages of Benjamin’s life looked similar, they created prosthetic busts of Brad Pitt at various ages for the actors to wear. For other sequences, Pitt himself had prosthesis and makeup applied to make him older. There is only a short period of time in the film where Pitt plays himself without effects to make him look older or younger. 

I also looked into makeup used in Avatar as it also used the same technology as Benjamin Button. As the makeup department head of Avatar. Tegan worked closely with James Cameron and Weta Digital to create makeup that would work with the new technology being used. Her unique skills, involving the use of specialized makeup, lead to the creation of Tegan's virtual makeup lab MoCap Fx. There, she created the unique phosphorescent makeup used to capture the amazing images you see in 3D on Avatar. 

Here is a walk through video with the makeup artist Greg Cammon for Benjamin button 
https://www.youtube.com/watch?v=7tQoEJYFjwY

References: 

Figure 1: Den of Geek (2009) 
    http://www.denofgeek.com/us/movies/14593/ed-ulbrich-behind-the-extraordinary-visual-effects-of-benjamin-button

Figure 2: FX Guide (2009) 
    https://www.fxguide.com/featured/the_curious_case_of_aging_visual_effects/

Figure 3: Digital Spy (2017) 
    http://www.digitalspy.com/movies/avatar/news/a843698/avatar-sequels-underwater-mo-cap/

Babbage R. Digital spy (2017) Retrieved from:
    http://www.digitalspy.com/movies/avatar/news/a843698/avatar-sequels-underwater-mo-cap/

Seymour M. FX Guide (2009) Retrieved from:
      https://www.fxguide.com/featured/the_curious_case_of_aging_visual_effects/

Staff , Runway (2010) Retrieved from: 
      http://www.runwaylive.com/3095-meet-tegan-taylor-the-make-up-artist-behind-avatar.html

Mclean T. Vanity (2008) Retrieved from: 
        http://variety.com/2008/film/awards/creating-the-look-the-curious-case-of-benjamin-button-1117997242/

Rositas111, Greg Cannom - Makeup artist of The curious case of Benjamin button (2008) Retrieved from: YouTube 
https://www.youtube.com/watch?v=7tQoEJYFjwY