This is an interesting 13 minute video about the imaging technology that was used in the movie "The Irishman" to make the actors (DeNiro, Pesci, Pacino) look much younger in scenes where they played younger versions of themselves.
While it gives many examples, it does not say much about the actual method, other that a brief mention that 3 cameras are used, two of which are infrared. Apparently the infrared frames are somehow combined with the real frames to soften skin, remove shadows, etc.
https://youtu.be/OF-lElIlZM0