There is no one perfect or guaranteed way to cook a brisket and the only assurance of good quality in the cook is, to be brutally honest, experience. Here are what I have found to be good "assurers" of excellence in brisket:
1. Whole packers will come out more moist than flats. This has been my experience in cooking probably sixty briskets. I've had some flats come out "acceptable" but the really fantastic ones I've had have been packers. I think the extra fat content and thickness really help.
2. Inject. Particularly the flat portion. Injection is insurance for moisture. Use lots of small, closely spaced injections both deep and shallow. Don't try to add a lot of flavor. Brisket has its own wonderful, beefy flavor and you don't want to override that. Commercial injections like Butcher's and FAB are my favorites but a can of beef broth with just a wee bit of added salt and maybe a tinge of onion and garlic will work, too.
3. Foil at 120-140 degrees. You don't HAVE TO foil, but it is more insurance for moisture. The hot brisket in the foil will, indeed, braise in its own juices and tenderize. This also avoids the dreaded "stall" where the meat chunk refuses to increase in internal temperature because it is giving off moisture. There are methods of producing tender, moist brisket without foiling but I've not had as much success with them.
Mops contribute to bark production more than anything else. If you like bark on your brisket, mop. Otherwise don't mess with it.
Water pans are necessary only in vertical tube cookers and serve to block drippings from putting out the fire. Pellet cookers don't need them and, at smoking temperatures, water pans don't add any moisture anyway.
I cook and recommend cooking fat side down, trimming to the point where about 1/8 to 1/4 inch remains on the fat side. I used to do the opposite but have gotten better moisture fat down.
Perhaps the biggest risk we take in brisket cookery is the brisket itself. Quality can be inconsistent among suppliers and butchers. It can be hard to find good ones. I did a Sams Club brisket last weekend that was purported to be select grade Angus. It was fatty and inconsistent. Would love to find a good, reliable source of briskets but never have.
Hub