I usually find US-75/I-45 to be the best way through, north to south, then use I-20 across the south side if connecting to a different route.
If coming from Oklahoma City, 35W through Fort Worth, just take my lumps on what the traffic turns out to be, it is still usually better than 35E or 635 at the same time of day.
I have some "totally avoid Dallas by at least 50 miles" routes, east and west, depending on your actual Texas destination. Hugo, Paris, Palestine, Crockett, Huntsvill, for example, going to Houston.
Doesn't work so well for Ennis, since it is already closer than 50 to Dallas, but Texas highway 34 (from Greenville) is far enough out to not be clogged with suburban traffic, you can get there on Texas 24 out of Paris.
