Usually I trim the fat cap to 1/4", rub it the night before, wrap tightly in plastic wrap, and refrigerate. Unless you plan on doing a basic salt & pepper, then you can rub just prior to putting it on the bbq.
I smoke at a temp of 225° to 240° until it reaches an internal temperature of 195°. Or, try the toothpick test: when done, a toothpick should be able to slide into it like warm butter. Every chunk of meat is different, but a good rule of thumb is 1-1/2 hours per pound. You can't rush it. I've had a 15 lb brisket take over 25 hours. Good woods to use with beef are oak, cherry, pecan, or hickory if you use it judiciously.
Pull it off when ready, double or triple wrap it in foil (if you haven't done so already), wrap again in towels, and place the whole thing in an empty ice chest, to rest for a few hours. Slice immediately before serving.