Learning to make fake breasts can be a helpful skill if you are trying to construct a realistic Halloween or theatre costume, or are just trying to make your Saturday nightdress fit better. The supplies don't cost much, and it doesn't take much effort to whip them into shape.
Buy a large bra and stuff it with socks. Remember, though, that socks are not easy to manipulate and form into believable-looking breasts.
Stretch a round, helium-quality balloon and insert a funnel. Fill it with the amount of grain rice or birdseed that gives you the bra size you want. Two cups of rice equal a "C" cup, and roughly 2 1/2 to 3 cups of rice equals a "D."
Fill nylons at their toe end with grain rice, then cut them to the size you want and tie them off.
Fill a balloon with liquid gelatin, then put it in the refrigerator and wait for it to solidify.
Secure an ace bandage around your chest with a safety pin. Then stuff socks, nylons or balloons in the bandage, creating the appearance of cleavage.