From The Verge:
As of The Last Jedi, Suotamo became the new full-time Chewbacca, and in Solo: A Star Wars Story, he plays the Wookiee again at a much earlier time in his life when he first met longtime partner Han Solo (Alden Ehrenreich) and they started adventuring together. For Suotamo, playing Chewbacca isn’t just about turning up on set in costume. He closely studied and shadowed Mayhew on film and on the set, and he eagerly talks about his complicated choices in bringing across the character through physical movement and vocal inflections. I sat down with Suotamo in Chicago to talk about the secrets of how Chewbacca’s mask works, the script that lays out what Chewie is saying in English, and what most people assume about his costume.
Is any part of the mask animatronic? Do you control everything about it?
It’s all just mechanical. The lower jaw is pushed down by my actual jaw. When the mouth opens, it pulls the upper lip down, with a coil, into a snarl. It’s all mechanical. It’s actually kind of heavy, and my jaw is always sore after a day’s work if I have to do a lot of [vocalizing]. So every mouth opening is heavy work. The head is held together by Velcro and all kinds of things, and you’re pushing all of that down whenever [Chewbacca groan noise].