Many people I know start their smoked briskets with a good, strong marinade. The marinade not only adds flavor, but helps start the process of tenderization to make the most of the smoking process. Think of a brisket marinade as kind of like a powerful rub that can sink into meat better than any powder mixture. Of course after you pull the brisket from the marinade you will still want to hit it with a great brisket rub to create that wonderful barbecue bark.
Try one or all of the Top 10 Brisket Marinade Recipes