I love learning about different dialects and I own all sorts of regional and time-period slang dictionaries. I often browse through relevant ones while writing a story. I also read a lot of diaries and oral histories.
Dictionaries are like watches the worst is better than none and the best cannot be expected to go quite true.
With acting you wanna see if you can get into trouble without knowing how you're gonna get out of it. It's like the exact opposite of war where you need an exit strategy. When you're acting you should get all the way into trouble with no exit strategy and have the cameras rolling.