We've done a LOT of briskets for comps and those recipes for rubs and injections are complicated.
Last weekend, I did a brisket at home and went REAL simple and I have to tell you it was probably the best one I've done yet. Great flavor, but simple.
INJECTION: I took 2 cups of hot water and stirred in 2 TBS of beef bullion and added 1 TBS each of garlic powder and onion powder. I injected throughout the flat mostly, but some in the point too.
RUB: I put down a light layer of Lawry's seasoning salt, then a REAL light layer of kosher salt, then a nice heavy layer of restaurant (med grind) black pepper.
I used hickory and oak for smoke. I think beef does really well with either of these, even a little mesquite. Stronger smoke flavors like hickory, oak, mesquite, etc, work well to compliment beef. I cooked the brisket for about 6 hours at 250. When I checked it, it had a nice dark color so I wrapped in in butcher paper. Foil works too, but I have been playing with butcher paper a lot lately and like the results.
The brisket ended up getting to probe tenderness (which ended up around 195-200 depending where I stuck the probe) at about the 11 hour mark. Your results will most definitely vary. I think I dialed down the cooker temp to about 235 after I wrapped, but don't remember.
You can cook a mighty fine brisket at 225 and an equally good one at 325. The only real difference is that the cook time will change depending on the temp. Adjust as necessary.
I've tried MANY different rubs on brisket and have done many without any injection. Some came out salty, some just OK, and some came out fantastic. All I know is that injecting with this simple flavor really helped get some flavor in the meat. I think a simple S&P rub works REALLY well on brisket. I've also tried a light layer of granulated garlic too.
Personally, I think the bottom line is that a well cooked brisket with a simple rub is a beautiful thing. Overcomplicating it will just be......well.......overcomplicated.
Good luck!