Put the masa harina in a bowl and gradually stir in 1 c. plus 2 TBSP warm water with a fork.
Add 3-4 more tablespoons of water, 1 at a time, and mix with your hands until the dough comes together.
Knead the dough until it is soft and pliable, then gather in a ball, cover with plastic wrap and set aside for 30 minutes.
Roll the dough into ping-pong size balls, moisten your hands with water to keep the dough from sticking.
Place the balls on a baking sheet lined with plastic wrap; keep covered with more plastic wrap as you roll the rest of the dough.
Set a large griddle over 2 burners (or use 2 cast-iron skillets); heat one side to medium-low and the other to medium-high.
Cut a circle slightly larger than a tortilla press (or a coffee can) from a large re-sealable plastic bag; include the seam of the bag in your circle so that the two circles remain attached on one side.
Place a dough ball between the plastic rounds and flatten in the tortilla press into a 5 inch circle, about 1/8-inch thick.
Peel off the top piece of plastic, flip the tortilla onto your hand and peel off the bottom piece of plastic.
Ease the tortilla onto the cooler side of the griddle and cook until it is slightly dry around the edges and starts to peel away from the griddle, about 45 seconds.
Transfer to the hotter side of the grill, uncooked side down. Cook until speckled on the bottom, about 1 minute, then flip and cook until puffed in spots, about 1 more minute.
Stack them in a cloth lined basket and cover with the cloth or wrap in foil and keep warm in a 50 degree oven.