An hour before you start preparing your meat, make the brine: bring 2 quarts of water to a boil then remove from the heat. stir in sugar and salt until dissolved, about 1 minute, then add pickling spices. Let cool.
Trim any large caps of fat off your brisket (optional) then place in a snug fitting container with a lid.
Stir the pink salt into the brine, if using. Add the cooled brine until covered. You shouldn't need all the brine - discard the remainder. If you need a little more than 2qt, cover with cool water as needed, or make a new batch of brine if a lot.
Weigh the brisket down with a plate if needed. Seal and store in the fridge for 3 days. After 3 days, give the brisket a flip, and store another 3 days.
To cook: After 6 days, preheat your oven to 200ºF. Find an oven-proof pot (such as a dutch oven) large enough to hold your brisket and fill it halfway with water. Set it over high heat. Carefully remove the brisket from its container and give it a good rinse. Add brisket and the remaining 3 tablespoons of pickling spice and wait until the pot comes to a boil, then transfer to oven and braise for 4 hours.
Remove the brisket from the braising liquid from and slice. Store brisket with the braising liquid and reheat together to retain maximum moisture, avoiding a boil. Brisket keeps for 3-5 days in the fridge.