If you are buying a "Corned" brisket, most of the recipes I have call for "mixed pickling spices" and maybe some cracked peppercorns. Starting from scratch is a "whole 'nother story" and I suggest an online search.
BTW, if you can find a "Corned" tri tip roast, you'll never go back to brisket! Years ago I did business with a small butcher shop that did his own tri tips. Man do I miss that shop!