Dunno about the other tools, but with the Gizmo it was pretty easy. It has a duck-bill apparatus that you open up, insert the pleat, and squeeze. Or, as B&D says:

It can also be used for pressing--either as a traditional iron or by using the creasing function to give sharp creases to pant legs, collars, cuffs, and more. Simply hang the garment on a hanger or lay it on a flat surface. Squeeze the pressing plates lever to open the plates and insert the area to be creased between the plates.