Thanks, everyone. I had read somewhere that breaking the foil seal was bad as it released the moisture it was trapping. Obviously, based on your experience, that won't be a problem.
One other thing I just thought of, if I apply the rub tonight, and inject tomorrow morning before cooking, will the injection wash away the rub? I just saw another video of someone injecting a brisket and the juices were seaping back out all over the place :( If that is a risk, perhaps I should inject and rub tonight. Any reason not to?