In this vintage 1958 video, Walt Disney reads from Robert Henri's The Art Spirit as he introduces some of the artists who worked on the Sleeping Beauty production.
(Video link) Disney explains the importance of an artist's individual style, but also how each member of the team must set aside his personal vision to match the style of the studio production.
Later in the video, Marc Davis, Eyvind Earle, Walter Peregoy, and Joshua Meador, go outdoors to paint a live oak, each one in a different style, each one explaining his intentions. Some paint squatting on the ground with their canvases propped awkwardly on rocks. At 9:29, Eyvind Earle shows how he mixes his caseins in cups. Meador uses highly flammable lighter fluid with his oil paint. Glad he's not smoking!
Book: The Art Spirit
The Art Disney's Snow White
Sleeping Beauty background art online gallery
Thanks, Andrew Sides