Oh, heavens, there are two accents that always stump me when I have to produce them: Scottish and Australian.
Bit of a diversion: It, Chapter Two features two actors I know. Taylor, who plays Don Hagarty, the boyfriend of the young gay man thrown off the bridge in the opening sequence, comes from my theatre company here in Utah. We were in shows together when he was a teenager. And Nic, who plays Henry Bowers, lives part-time in a Salt Lake City suburb and moves in some of the same social circles as I. Also, I was in the 1990s television miniseries adaptation of Stephen King's The Stand (oddly and newly relevant now), so we share a bit of that too. Most of "Denver" was shot in my neighborhood. Nic is Australian, and he nails the American accent perfectly in the movie. And he's been very patient with me when I try to grasp the physiology of Australian speech.
I've been trying to teach him the finer points of Utah's accent. Sydney as "seed knee" makes so much more sense now, because one feature of the Utah accent is to reverse that. We broaden and slacken the eccentric vowels. "Well" (as an interjection) is pronounced "wuhl." And "feel" is pronounced "fill." "My" is "muh." "To" is "tuh." The one thing he takes to effortlessly is our glottals, which are common in, well, the Commonwealth, but fairly rare in American. In Utah, the city name Layton is said "Lay'un." Those things jutting up all around us are "mou'ins."
If you find video of our former governor, Michael Leavitt, you can hear a mild, genteel Utah accent. He served in national administrations as well, so there's plenty of video of him. Pay special attention to the subtle shapes of some of the vowels. That's hard for non-natives to grasp, but it's very distinctive to the attuned ear. But the real treat is if you can find audio of his wife, Jackie. (Yes, Utah had a First Lady named Jackie.) She has a strong northern Utah accent, which is both highly localized and almost comical in the same sort of lingual strictures that I hear in some Australian accents.