Hey SC, that's why "they" say brisket is one of the hardest meats to smoke (hehe). Ed is certainly right about injecting and letting sit overnight in the fridge to "get happy!" Brisket is a very tough cut of meat, and can certainly dry-out.
With that said, I believe one thing that might have led to your dry meat is
too much intervention! These smokers cook very differently from stick burners, or any other "traditional" smoker (charcoal, gas, wood...). What you will probably find out is that you really don't have to babysit them to get good Q out of them. Every single time you open the door, flip, spritz, fiddle, etc..., you disrupt the cooking process and release moisture.
Try this next time:
1. Prep your brisket the night before. Trim the fat cap to about 1/4" thick and score it to accept rub. Inject it with a beef injection. Check out the recipe section for brisket injections; there are several to suit your taste. Coat it with your favorite seasonings or dry rub, wrap and place in the fridge. Here's an injection I use:
1/2 cup beef broth
1/4 cup Worcestershire
2 tblsp crystal hot sauce
2 tblsp demerara sugar
1 tblsp salt
1/3 cup Foster's beer (or any other full-flavor beer)
2. The next morning, prep your smoker and add the wood. I personally like straight hickory, or hickory/cherry for brisket, but that's my taste - find yours.
3. Remove the brisket from the fridge and place on a shelf. You can add a little more rub, if you wish, but the meat is already well-seasoned.
4. Place the brisket in the cold smoker fat-side-up with a water pan (or soup can) in the bottom filled with apple juice or beer (about 1/2 way). Set up your thermometer in the meat (the Maverick 732 rocks). Set the temp to 225.
5. Go drink coffee, watch t.v., take a nap....you get the idea.
6. Monitor your temps, and make sure (every now and then) you see smoke coming out of the blow hole.
7. Wait for the briskie to hit 200 internal (count on about 1 1/2 hours per pound).
8. At 200, remove and double-wrap in foil for a rest. Place in a cooler with a heavy towel over it. The resting period is
very important for brisket! (at least, I've found).
9. After at least 1 hour (1 1/2 to 2 is even better), pull that bad boy out and carve it against the grain! Use a really sharp knife because it will fall apart due to moisture and tenderness with a dull knife!
10. Final step - fill yourselves, and relish in the praise and accolades you'll surely receive for such an incredible brisket!!
Sometimes, it's natural to make things much harder than they need to be. One thing I've learned about these smokers is that minimal intervention is the key! They will produce good Q despite us! Great temp-controlled, moist environment - vastly different from traditional smokers!
Here's a link to my last one, if it helps:
http://smokinitforums.com/index.php?topic=979.0