When anyone in the field of cartoon voices is asked who the good teachers are for studying that craft, the answer — whatever it is — is usually preceded by, "Well, the best was the late Daws Butler but…"
Daws was not only one of the most talented actors (voice or otherwise) but an exceptional tutor, as well. You can't study with him but you can absorb some of his teachings in a forthcoming book called Scenes for Actors and Voices. Ben Ohmart and Joe Bevilacqua have collected many of his scripts, exercises and theories in what will surely be a must-have item for anyone interested in acting for animation — and probably acting anywhere. It's scheduled for a June release but you can get your order in now by visiting their website.