One of the great qualities of pastel as a medium is its versatility in "mark-making." One of my favorite ways to use it is to brush the side of the pastel stick over the surface of the ground - in particular, a sanded ground. This not only gives a quick and complete covering of the area if you wish that effect, but when the stick is gently glided over existing color, it can also "texture-ize" (marble-ize, scumble-ize (?)) the colors leaving a mottled look. I love this effect and it's fun to do.