Well, that's a start.
Seriously, a good rub will draw moisture to the surface in order to make a "bark" and will also penetrate to tenderize.
I use paprika and black pepper and salt.
And a few other things...in classified quantities.
The exact nature of which, if disclosed, would result in my having to kill those to which it was disclosed.
Briskets are extremely touchy.
The majority of mine are simply thin-sliced and eaten on freshly baked sourdough bread.
The one's I screw up...become chopped BBQ for hamburger buns, which I immediately disavow any knowledge of.