Here are a few brief but interesting excerpts from a transcript I made years ago of the late June Foray's hour-long voice acting seminar that she presented a number of times at the San Diego Comic Con including here, from the late 1980s.
“When you're on-camera, you have to have your pictures. That's de rigueur. But when you just do voiceovers, it's a tape. So if you say...They don't use too many dialects anymore. There are so many segments of society that become angry at doing an accent. But you'll find the common accepted ones. French. Because you have the French chef. Some nasal who comes from Paris. Or Italian. Mel Blanc did...not Taco Bell... Frito-Lay a long time. He did a Mexican accent but he deed (sic) a sing-song of it and it wass (sic) the right one and the Mexicans raised hell about it. So they don't use too many dialects but if you do, do one GOOD one--say French or Italian--just to show your versatility.”
“You know what Daws Butler used to do and I used to admire Daws for doing this? He made a list of all of the characters and somebody would say, ‘Daws, I need a giraffe,’ or ‘I need a pencil,’ or some inanimate object. You're asked to do things like that! Frying pans! Anything! It's crazy, what starts talking! So Daws always kept a list. This voice, this voice, this voice...and sometimes if you can't think off the top of your head just surreptitiously take the paper and look at it and say, ‘Y'know, this voice might be great.’ If you can do impersonations, but maybe they aren't just right, get the idea of that voice and don't SAY it's an impersonation! Daws, in Cap'n Crunch...when he was Cap'n Crunch...There was a character actor named Charlie Butterworth and Daws copied his voice. He's long since been dead. Many, many years! And when, of course, Jay Ward did that...produced it, Daws came in and said, ‘You know what would be a great idea?’ and nobody had done it or even thought about it or maybe even knew about him and he came up with that voice and it was perfect!”