Poke small holes in the fat cap of the tri-tip with the tip of a sharp knife. Cut the garlic into thick slices and put half the slices into the holes, pressing them in so that the garlic fits into the meat without protruding. Flip the tri-tip over and repeat on the other side with the remaining garlic. Mix the salt and pepper together and rub it onto the meat, making sure to use the entire mixture. Let the meat sit and absorb the rub for at least 20 minutes or (preferably) refrigerate it, covered, overnight. Bring it to room temperature before cooking.
Heat the wood or charcoal grill to high or a gas grill to medium-high. (If you're working with charcoal or wood, you should have it very hot, white coals and only a few final flames; if you're using the gas, temperature should be 350 degrees and the lid should be closed.) Put the soy sauce, olive oil, and wine into a spray bottle and shake well to combine.
Put the tri-tip on the grill fat side down, 12 to 15 inches away from the coals. (Pile the coals to the side of the grill if necessary). Cook the meat without flipping it, spraying on a little bit of the soy-oil-wine mixture every 5 to 10 minutes until the fat cap is golden brown, 10 to 15 minutes. Flip the meat, and continue cooking, using the spray, until the tri-tip is about 125 at the degrees at the thickest part, 30 40 minutes for rare (or your desired doneness); (and less than that on a gas grill). After the meat sits, it will come up a few degrees in temperature and will be medium rare at the center and well done around the edges. Let the meat rest for 10 minutes, then cut into 1-to2-inch thick slices.
