I've never done a salt/pepper only rub for a brisket, but I've had it and it can be amazing. This guy suggests a 1:1 salt

epper ratio, with about 1/2 cup of each for a 10-12 pound brisket. That sounds about right to me. You sprinkle pretty liberally.
http://putneyfarm.com/2013/09/14/bbq...ranklin-style/