Helene Stanley/ Cinderella

Actress Helene Stanley acted out all of Cinderella's scenes for the animators. Here she takes an imaginary shower at the beginning of the film.
This requires the same acting talent as scenes that would be a live action/animation combination such as Mary Poppins and Roger Rabbit.
Here Stanley throws her robe backward over a divider. Birds catch it during the final scene. Then she imagines a cold water splash coming from a wet sponge, also carried by birds.

You can compare final frames to live action photostats, which have been drawn over by a layout artist, who added birds, props as well as ideas for environment.

This gag didn't make it into the movie. A little bird who was standing by, got drenched during the splash. He shakes off the water and is visibly displeased. Cinderella reacts sympathetically to the little guy.

It is obvious why Disney had Stanley act out other animated parts such as Sleeping Beauty and Anita in 101 Dalmatians. She completely understands what animators are looking for. Clear poses and movement that reveals the character's thinking and personality. It would be easy to over- or underact those scenes.