How do I go about getting my trims in check
You shouldnt have to. Trims do stuff.. its what happens. If they are doing dumb stuff then you have a mechanical issue (maybe your maf tube is stupid) so you will have to adjust a bit... as said before its easier to do that outside of the maf table typically.

Especially the tuner guide contradicts some.
Don't a lot of people modifty the maf table to get the trims in check?
Every tuner guide made is completely wrong. Dont look at them for any value. People that "tune" are also not experts in any form... the guys that write the HPT software in fact have no idea what they are doing unless they spend significant time looking at complicated de-compiled assembly code. Even at that point its hard to see a clear picture of whats going on.

Where this "tune fuel trims to 0" idea came from is just stupid if you think logically about it.