Combine the kosher salt and black pepper (coarsely ground, about 16-mesh) in a medium bowl and whisk until evenly blended, about 30 seconds.
Use immediately to season a trimmed whole brisket: sprinkle a light, even layer on all sides and edges, then pat to adhere.
Let the seasoned meat rest 15–30 minutes at room temperature until the surface looks slightly moist before cooking, or refrigerate up to 12 hours for deeper adhesion.
For storage, transfer any unused rub to an airtight jar, label, and keep in a cool, dark place up to 1 month; shake before each use.
For batch scaling, maintain a 1:1 ratio by volume; mix only what you can use within a month for peak aroma.