In a large bowl combine the flour, wheat bran, wheat germ, baking powder, salt, and mix well. Add vegetable shortening and use your fingers to to rub the shortening into the flour mixture until completely incorporated.
Pour water in and mix with a fork until. If the dough is too dry, add a bit more water.
Scoop mixture out into a cutting board and knead until smooth (about 3-4 minutes). The dough should be soft and stretchy, but not as soft as bread dough.
Cover dough with plastic wrap and let rest for at least 1 hour. (The longer the dough rests the softer your tortillas will be.)
Divide the dough into 12 equal pieces and roll into balls. Heat a cast iron skillet or comal to medium-high heat.
Sprinkle flour on your work surface, flatten the ball of dough with your hand. Using a rolling pin, begin to roll back and forth across the ball, rotating it slightly each time, and sprinkling more flour as necessary, until the dough has stretched out to make a large thin circle. Try to roll it as thin as you possibly can.
Lay the tortilla on the comal and flip after 30 to 40 seconds The tortilla should bubble up almost immediately. Cook 30 more seconds on the other side and remove from pan. Be careful not to overcook the tortillas or they will become crisp. Remove tortillas from pan and place in a tortilla warmer or kitchen towel.
Repeat this process with the rest of the dough.