1 extra-large cooler (3 to 4 feet long) La Caja China roasting box 2 1/2 16-to-18-pound bags charcoal
Make the brine: Combine the citrus juices and rinds, jalapenos, cilantro, salt, ice and 8 gallons water in the cooler and mix until well combined. Add the pig belly-side up, making sure it is submerged. Place the cooler in a cool place to brine for 24 hours.
Set up the La Caja China according to the directions. Remove the pig from the brine; pat it dry. Arrange it between the 2 grates of the La Caja China, using the hooks to secure. Place in the box skin-side down.
Place the ash pan and charcoal grid on top of the box, then pile 16 pounds of coals on top and ignite. Spread out the coals and let cook, undisturbed, until the meat is cooked through, about 3 hours, adding more coals every hour.
Carefully open the La Caja China. Using heatproof gloves, flip the pig (and the grates) so it is skin-side up. Use a sharp knife to score X's in the skin, being careful not to pierce through to the meat. Place the top back on the box. Cook until the skin is crisp, about 45 more minutes. Let rest at least 20 minutes.