Chalk-type furniture paints require a sealer of some sort, usually a water-based polyurethane or wax. For painted upholstery work, our best results have been gained with wax. Both of the companies listed above sell waxes of their own formulations, but any furniture paste wax should do okay. Ask anyone that paints furniture and they will tell you their favorite wax for one reason or the next. Try a few and make your own mind up. Apply the wax liberally. Allow it to dry, and then rub, and then rub some more to burnish the surface. Terry cloth towels work well for the burnishing step.