Fix the tube in place; roll outward the upper part of the bag so as to put the mixture just above the tube without smearing the sides of the bag. Fill the bag about one third full. With the right hand carefully twist the bag above the mixture, guide the tube with the left hand, and force out the mixture by continuing the twisting, at the same time using pressure, with the right hand. To form a star, hold the bag in vertical position and press out a sufficient quantity of the mixture. Separate the tube from the material by pressing the tube downward slightly and raising it quickly. For other designs hold the bag at other angles, between the vertical and a horizontal position.