Beat the egg whites in a large stand mixer fitted with a paddle attachment on high speed for about 10 seconds to break them up. Reduce the speed to low and gradually add the confectioners' sugar. When all of the sugar has been incorporated, increase the speed to medium and beat the mixture until it thickens and holds a soft peak when scooped out of the bowl, about 2 minutes.
Reduce the mixer speed to low and gradually sprinkle the tylose powder over the mixture. Beat until the mixture thickens to a moldable consistency (increase the speed of the mixer to high as needed if the machine is struggling on a low speed), about 15 seconds.
Dust a work surface with a light coating of sugar and coat your hands with the vegetable shortening. Turn the mixture out onto the surface and gently knead it just until it forms a smooth, soft dough that is not sticky.
Transfer the finished dough to a resealable plastic bag, squeezing out all of the air. Put the plastic bag inside of a second resealable plastic bag, again squeezing out all of the air. Let the dough rest in the refrigerator for 24 hours before using.
Color and shape according to your favorite shoes!
If you want to color your dough, add the coloring paste, gel or liquid right after the addition of the tylose powder, making it a shade darker than the desired color.