Heat a non-stick skillet or comal over medium-low heat. You may also use the grill. Once hot, after 3 or 4 minutes, layer 2 flour tortillas, the cheese slices and the Chicken Tinga. Place 2 flour tortillas on top of the open ones, and let them cook until the tortilla on the bottom has begun to harden a bit. Flip to the other side with the help of a cooking spatula and let the quesdillas continue to warm up, until the cheese has completely melted and the tortillas have hardened on both sides.