just my two cents on this.
Although living in Nebraska now I was born and bred in the Republic of Texas where brisket is king. A good rub is key and everyone has their personal favorite but dont get carried away with the amount you use. We arent smoking ribs here. Let it sit overnight if you can to give time for the rub to do its magic. I inject my briskets with plain beef broth or stock. About 3/4 c for a packer trim brisket. Helps add a little moisture to a dry piece of meat.
Dont get too hung up on the temperature of the meat to determine doneness. I smoke based on weight. 225-250 for 45 minutes to the pound. Mesquite smoke for the first three hours, thats it. then just coals or heat. At this point wrap tightly in heavy foil and seal the best you can. Continue cooking. Remove foil 30 minutes before time is up to allow outside to crisp up a little, this step is optional. Allow brisket to rest for several minutes before cutting and serving.
Heat, light smoke, and foil are key. Also, if you arent ready to eat when the brisket is, put in a covered dish in a cooler and then fill remaining space in cooler with towels, paper, blankets or whatever you have. Will stay hot for 3-4 hours without overcooking
C