The dialect coach talked about how to do a southern accent and was mostly right, though her accent she used when demonstrating still sounded a bit fake. It was or less half-pronouncing the letter i in words, and dropping the letter g off the end of words. What she didn't get right is that we also talk a bit slower than others, due to being more laid back.

In Radio Broadcasting, we were taught how to speak `General American'. I haven't used that knowledge much since I graduated 30 years ago (literally. Class of 1989),  because its a royal pain to do. I actually have to speak about 20% slower when doing so. (Basically, pronouncing i fully, not dropping the g off words, over-enunciating and better diction, but there's more to it than that.)

As for the not pronouncing the letter i, there's no really way to spell it out in written form, but its true. Marvel had Cannonball, who is supposed to be from Kentucky, say `Ah' in place of `I' when talking about himself,  but that's not correct. He sounds like he has a speech impediment more than a southern accent! I shudder to hear how he'll sound in that New Mutants movie.....

Sadly, I've never seen the Bob & Doug animated show that was done about 10 years ago. But with Dave Coulier substituing for Rick Moranis, I'm not sure I want to......

Speaking of accents, here's a funny scene (starting at the 1:30 mark in the video clip) where Alan Partridge (Steve Coogan) tries to understand his friend Michael's Geordie accent:

Anyone from New York, here?  I've heard that the accents change from borough to borough so, for instance, someone from Brooklyn could tell another person is from the Bronx?

I wlll admit that I can definitely tell when some one is from the East End but not necessarily from North, South or West London.