“Grapes of Wrath”: Dialect Coaching
CHICHESTER OBSERVER: THE GRAPES OF WRATH
Interview with Julia Wilson-Dickson, dialect coach
“(…) If the accents are authentically Oklahoma and just as importantly consistently so, then there’s a good reason buried in your programme. (…)”
While the first paragraph of the article is a wee bit at odds with the reviews, this makes for interesting reading. It will give you some insight into the work of a dialect coach.

Rehearsal for "The Grapes of Wrath" at Chichester Festival Theatre. (c) CFT