Love the brisket discussion here. I have a full brisket from my 1/2 beef that I need to get done. Takes up a lot of freezer space! Maybe I'll do that this weekend if weather is nice.
Typical trimmed brisket from a meat counter is probably fine, but one mistake I've made for a full packer brisket is if the butcher didn't trim much fat, I wasn't aggressive enough in removing most of that fat. You don't need it, and frankly don't want much fat cap at all. There are a few videos to help with this.
Other than that, once you do your own brisket, you might be ruined from ordering it in a BBQ restaurant ever again. As in, you still will order it because brisket is awesome, but you'll probably be disappointed in all but the elite places (Whatcha Smokin' in Luther always nails it). Doing brisket yourself is time intensive, but it's probably the best set of meat you will get off your smoker. Delicious. 1000% better than the brisket you'll get in most BBQ joints. Just take your time and take it off at that 200-203 range and you'll love it.
Oh and I definitely recommend letting it rest AT LEAST 30 minutes after you take it off the pit (if you're in a hurry) and 60 minutes is probably the better minimum, so plan accordingly.
Typically because it's unpredictable for a long cook, if I'm smoking for a set serve time I will start this in the evening the night before I want to serve so I probably hit the stall around the early AM next day. Wrap in my butcher paper then keep going to finish. I'll likely finish well ahead of serving time. Take off the pit and rest inside a towel (still wrapped) for ~1 hour. Then wrap with another towel or two and into a cooler to keep warm until I want to slice and serve, up to several hours later. It's always been awesome.
