I have found over the years that the rubs and sauces don't add a lot to smoked brisket. Nothing adds to a smoked brisket like time spent over a good hard wood fire.
The system I have worked out is unbelievably simple. When I do brisket and ribs for a big cookout, I do use some type of rub or powder. I liberally cover the brisket, but only lightly cover the ribs. I put the briskets in the smoker (fat side up of course) for 4-6 hours while keeping the temp around 250-275. During the last couple of hours, I throw the ribs in the oven in a covered pan to pre-bake them. When the rib meat begins to draw back from the bone, I switch out with the briskets. Ribs on the smoker, briskets (covered) in the oven at about the same temps. This will finish the briskets making them super tender without drying them out.
The ribs only need 60-90 minutes on the smoker. About half way through, I hit 'em with some kind of mopping sauce. My favorite is a mixture of Heinz 57 and honey. Pre-baking will make them tender 'fall off the bone' good. Smokiung will give that flavor you can't get anywhere else. Mopping will keep them from drying out. The sauce will dry to a sticky texture over the 30-40 minutes. Take 'em off, cover up and let 'em sit for a little while. Don't try to cut them right away. Let 'em rest.
Back to the briskets; Take them out of the oven and let them rest covered too. If you want those nice pretty slices like you see in the restaurants, you have to let it rest. I usually give it about an hour.
I almost always throw some sausage or brats on the smoker, fitting them in wherever I can find space. Slice the sausage while the others are resting. Put them in a warming oven then git after the ribs and sausage. It's not unusual to spend an hour carving just to serve a group of 30 or so.
After that, just sit back and wait for the compliments. One thing I have learned well over the years is to never under estimate any groups ability to eat good BBQ. I usually double the portion sizes over any other type of meal I serve and I don't usually have a lot of left overs.
Hmmm.... Now I'm hungry.