Oh my god! How could you ruin a brisket like that!!!
You need to get a smoker. Don't double wrap it, you'll over cook it and BBQ sauce on brisket? God forbid! Sauce is for pork.
I do it pretty much as pictured above. I make a 1:1 mix of kosher salt and black pepper. I spread that liberally over the brisket. If the fat cap is to thick I'll trim some of that off. I then put it into my smoker for 4 to 5 hours and maintain a temp of about 225 deg F. My smoker is a step above the one pictured but still on the low end. After about 5 hours of smoking you'll have all the smoke flavor you'll need. I then put it on a broiler rack (no foil!!) and finish it off in the over at 250 deg F until it reaches and internal temp of 175. I then take it out of the oven and let it rest for about 20 minutes. Cook it low and slow all the way and you'll be amazed at how better both the flavor and texture are. My method looks pretty much as pictured above and is just a little easier. What ever you do don't cook at a temp higher than 250 deg F (fat cap up) and don't exceed an internal temp of 190. Past 190 and it becomes dry and crumbly. Cooked right when you pull on the ends of a slice it should be like a little accordion. It shouldn't fall apart and it should be tender to the bite and juicy.
Now my sister has a Traeger and that has enough temperature control that you can maintain a constant 225 deg F the entire time you're smoking it. I've made some killer brisket on her Traeger. I'm to cheap to spring $400 to buy one of my own. LOL