Marinate the steak: Cover the skirt steak with a piece of plastic wrap and pound to about 1/2-inch thickness with a meat mallet or rolling pin. Combine olive oil, salt, pepper, orange juice, lime juice, and garlic in a baking dish. Add steak and turn to coat in marinade. Leave at room temperature while you heat the grill, at least 30 minutes or up to an hour, turning in the marinade occasionally. 

Grill the steak: Heat a gas or charcoal grill over medium-high heat. Once grill is ready, clean the grill grates and douse a large wad of paper towels with oil. Grab the wad of paper towels with tongs and wipe the oil-soaked paper towel over the grill grates until they are coated in oil. 

Remove the steak from the marinade with tongs, letting the excess marinade drip back into the dish. Place on the grill and cover with the lid. Let cook, undisturbed until a crust forms on the bottom, about 2-3 minutes. Turn steak and continue cooking, covered, until steak is done to your likeness, about 3-4 more minutes for medium-rare. 

Remove steak to a cutting board and let rest 10 minutes. Cut into thin strips. 

Make the tortas: While the steak is resting, toast the bolillo halves on the grill. Place cut-side-down and watch carefully so they don't burn.

Spread 1 tablespoon of Roasted Poblano Salsa on each bolillo half, divide tomato slices, between 4 bottom sides of the bolillo halves, divide avocado between the top halves, then mash to spread avocado into an even layer. Sprinkle avocado and tomato slices with salt and pepper. Divide steak slices among the tortas, cover with top half of the bolillos, cut each torta in half and serve!