Here is what I do after going through the learning curve:
I cook at 225. I plan 1 hour to 1.5 hours per pound for packers.
I cook unwrapped for 3 to 4 hours. The meat will absorb little smoke after that time.
Here is where I use the "Texas Crutch". I place the brisket in an aluminum foil chaffing pan. I add enough beef base and water to cover the bottom, and then I seal the top with foil.
Back in at 225 until done. I try for 205 degrees internal temp, but I use small metal skewers for the "butter" test. I start testing at 190 degrees internal temp.
Once the beef tests correctly: into the cooler it goes for up to 3 hours to rest.
I know the old pros will say I am cheating, but I don't do competition BBQ. I get a good bark, good smoke and seasonings flavor, and the meat is fork-cut tender. When family and friends beg you to smoke brisket for the upcoming party, I would say one is doing okay.
As an additional note: I cooked 5 briskets at once one weekend for a large group event. (The Ol' Bandera was working hard that day!) Of the five briskets, one was done in 9 hours and the last one at 13 hours. All similar size, all same grade (Choice), but with very different cook times. It will be done when it is done, and it must be snatched out of the cooker in that window or it will become overdone and dry.
Hope this helps.