Hello all, new member here.
I've been smoking brisket since I was about 12 years old. The only time I have a problem (other than one really bad choice for wood) is when I don't leave it to cook long enough.
I grew up using the cheap Brinkman vertical water smokers. Now I have a cheap Char-Griller offset direct flow smoker.
Here's my method:
I buy the cheapest brisket I can find (and dang they are getting expensive these days--I remember when brisket used to be a $1.29/lb.) Usually I buy in the 13-14 lb. range just because of the number of people that I need to feed, though I do think that smaller briskets are inherently more tender. I usually end up trimming a couple of pounds of fat.
I use lump charcoal and hickory and apple wood.
I trim some of the fat, but leave a layer maybe an 1/8" thick. I don't use any rubs as I like to taste the meat and hickory smoke. I also put a couple of foil pans on the tray under the brisket with about a half gallon of water total. This is a hold over from my younger years growing up using those cheap water smokers. But I think it helps to control the temps inside the smoker and to keep the brisket moist as it cooks. I always cook with the fat up, and the start with the point facing the fire box, though I do turn it around a couple of times so that it cooks evenly.
I smoke at about 220-230 degrees under heavy smoke for at least 5 hours, sometimes 6 if it is a large brisket. I liberally mop a concentrated apple juice on the brisket about every hour. Then after 5 or 6 hours I will wrap it in foil, with a liberal application of my apple juice mop and then leave it to finish cooking. The brisket is usually in about the 160 degree range when I wrap it. Then I cook for another 4 or 5 hours just keeping the heat as steady as possible. I like my brisket to be above 190 degrees for at least an hour before I pull it off. It's usually a solid 200 degrees when I pull it off the smoker.
I don't usually let it "rest", but it usually sits for about an hour before cutting for the rest of the meal to be ready.
My briskets need a solid 10 hours of cooking, and more if they are larger. If I try to cook them faster, like to make a mid afternoon meal time, they are always tough and not as moist. As long as I cook them long enough, they are always moist and tender and fill your mouth with an explosion of smoke flavor when you bite into it.
And yeah, people in my family fight over the burnt ends
Here's a pic of one of my recent briskets.