I smoked a 14lb brisket. Unfortunately, it came out drier than usual. It was a USDA select, so I took a little bit of a gamble as it passed the flop test, but not much marbling. It was delicious with a nice smoke ring, but I usually do much better.
Yes, select is going to dry out a bit more than choice or prime.....not sure if I have even seen a prime brisket before.
Try it again. Use a tin of water and maybe some herbs....keep the humidity up. That way it won't cook off as much of the fat down in the grain of the beef.
The fat cap won't melt down as quickly. Can't say I have ever been a big fan of beef on the smoker except for a nice prime rib. I have smoked plenty of beef cuts over the years, but I tend to stick with pork or poultry. Just my choice, or maybe they just come out better for me.
Beef, a couple of filets or rib eyes seared in a scorching hot cast iron for a minute or two per side, finished in a 350 degree oven to the doneness you like...a dab of Maitre d's butter as they rest. As good as it gets IMO.