Mix buttermilk, soda, and salt in bowl -- stir well so the soda is not lumpy. Stir in enough flour to make a dough just thick enough to handle. It will probably take most of the 4 cups. Turn out on a floured board (I use wax paper over a newspaper, so I won't have to wash the board), and work in just enough flour to handle without being sticky. Roll out and cut, or I just usually "pinch" off and shape into biscuits. Have ample amount of shortening melted in pan. Dip biscuit and flip over so top of biscuit will be oiled. Bake in hot over (450) 15 to 20 minutes or until done. I like mine brown, flat, and a little chewy.
If you don't have buttermilk, you can add 1 teaspoon vinegar for each cup of sweet milk you use. Or if you prefer sweet milk biscuits, just leave out the soda and add 2 teaspoons baking powder. I have never been able to make good sweet milk biscuits. If you want them a little flakier, add 2 Tablespoons shortening to either kind.
I think Melissa is the champion biscuit eater -- with the possible exception of Steve.