This is where each one of us have our own particular detailed methods that work for us, but the basics are very similar. None of them are wrong or necessarily better than the other for each of us, just different and might change the outcome slightly or not in very small ways that suits each one of us better. Like using different spices in our rubs, or different woods. That is what is so great about this site, all of us sharing opinions for us to try. Then we can find what works best for each of us and share our experiences for others to consider.
Like me, I tried BP a couple times and it was too leaky and messy for me for the slight change in flavor it made for me, so I went back to easy with a double wrap of heavy foil and I am happy with that. Just me. I also have varied the resting time. One hour is the bare minimum for what works for me, I try to do a minimum of two hours when I can, I find it makes the meat more tender for me.
In my opinion with the "lean or more marbled" comment you might be thinking of something like serving custom sliced prime rib, which is a whole different animal than what I think you will be preparing and serving here. I am thinking a good smoked BBQ brisket sandwich with your friends selecting hot, or plain BBQ sauce to fit their taste buds with some sides as your neighbors come by out in your garage. Right? If it is tasty tender brisket, they are not going to be too particular of lean or marbled, sliced or chopped. Just my opinion.
Myself, the reflective foil keeps the heat in while insulated in the cooler resting. I throw a bath towel folded cooler size in the bottom. put the foiled brisket in the middle, put another folded towel on top and let it rest or "cure" if you will a couple hours. I then pull it out of the cooler, easily scrape off most of the fat while is hot and slice it all up across the grain. It will still be steaming after 3 hours. You can easily trim more fat off each slice after slicing if you like.
You will have some nice slices you will most likely cut in half for sandwich length and you will also have some "chopped" on your cutting board that go in the pot also to fish out with a slotted spoon to serve later. (Actually my favorite sandwich) This way you are handling it once on the cutting board, stacking it once in your crock pot and if it all does not fit, put the rest in a covered pan to keep warm in the 160' oven to refill your crock pot when needed later in the day. Keeping it covered will help keep the moisture in, be diligent at covering it in between serving if you have long pauses.
Again to me for Beginner Basics, pick a rub to try, Jeff's Rub is a good starting point, you can adjust it later to fine tune to your taste buds if you might like. Keep your smoker temp at least 225', don't get too excited if it varies up 20' at times, so what, some here do their entire smokes at 300' or more, but it is a little different style. Keep smoke rolling until it reaches 160' IT, then you can double wrap, again I use foil, and you can stop the smoke. Start probing around 200' IT. If you still have some tough spots, take another look in 30 min or so till it is all tender. Drop in the cooler at least an hour, longer does nothing negative. Slice across the grain, and enjoy now or package for later.
If you have time and the ability I would try to do a practice brisket this weekend for you and your family. You can zip lock the leftovers and put into the freezer for easy meals later. If you could do that, you will be way ahead of the game and get more relaxed sleep next weekend.
Hopefully some others will share their thoughts and tips also. Good luck to you
