I use Vital Wheat Gluten for anything bread-like. If I remember correctly, the gluten is what gives the dough the stretch that it needs to hold in the air bubbles for a better rise and adds to the "chew" of homemade bread. I use 1 tablespoon for a batch of pizza dough and 2 for a full batch of bread (which for me is 2 - 1 pound loaves). I have dough enhancer also but I prefer the wheat gluten. The dough enhancer was given to me by a friend who bought it for a recipe, made bread once, decided it was too much work, and gifted me all her supplies - yeast, bread flour, pans and bread stone. 
She received a warm loaf of bread about twice a month in exchange.

She received a warm loaf of bread about twice a month in exchange.
Sourdough is a tough one to tell how much flour to add since it will be s bit sticky even when stiff. Go by the stiffness of the dough
, but I do tap on the bottom to see if it sounds hollow. Then bake it another 5 minutes... I usually tend to pull it out a little too soon.