In pot large enough to hold brisket, combine 1 gallon of water with kosher salt, sugar, sodium nitrite, garlic and 2 tablespoons pickling spice. Bring to a simmer, stirring until salt and sugar are dissolved. Remove from heat and let cool to room temperature, then refrigerate until chilled.
Place brisket in brine, weighted with a plate to keep it submerged; cover. Refrigerate for 2 days if it’s thin, a third day if it’s thick.
Remove brisket from brine and rinse thoroughly. Refrigerate one more day uncovered.
Combine the rub (pepper and coriander) and coat the brisket with it. Smoke and cook the brisket, till tender, as described above. Slice thinly to serve. This will keep for a week in the refrigerated.