The technique of forming 2 round loaves at the same time is common in Germany, and seems less so in France. A skilled baker can form 2 round loaves, 1 in each hand, in about the time it takes to form 1 round loaf. Clearly, from the perspective of speed, it is a skill worth developing.
Begin by having 2 preshaped loaves on the work surface, good sides down. The fingers of each hand are responsible for folding over a new flap of dough, while the heel of each hand has the job of kneading and rotating the dough piece. Place 4 fingers of each hand on the back side of the dough piece; the thumb remains in front. The fingers fold approximately 20 to 25 percent of the dough over into the center. The heel of the hand then rolls the dough away from you, kneading the folded flap of dough. During this stroke, the heel of the hand also makes a slight rotation of the dough (the dough in the right hand rotates counterclockwise, and the dough in the left clockwise). Once rolled and kneaded, the fingers, still behind the dough piece, fold another flap of dough forward, and the heel of the hand repeats the rolling and kneading stroke. By continuing the rotation of the dough piece, the heel of the hand enables the fingers to fold a new portion of dough to the center. In this way, the entire piece gets evenly worked. Just as there is an axis to the dough when forming one round loaf, so too there is an axis to the loaves when forming two at once. While it is possible to form the loaves completely with this method, it is generally preferable to bring the loaves to 80 to 90 percent completion, and then to finish the rounding in the same manner that one loaf is finished, with a few quick strokes to tighten each loaf completely.