There is no doubt that painting over marble can be challenging, but only if you do it the old-fashioned way, with hours of preliminary sanding. With Chalk Paint, you can cover marble in one or two coats with little to no sanding beforehand. Chalk Paint was invented by painter Annie Sloan, who is widely credited with transforming the art of decorative painting with the publication of her book "Annie Sloan's Complete Book of Decorative Paint Finishes."
Conduct a trial run with Chalk Paint before you apply it to the marble. Ideally, you can apply it to an inconspicuous place on the marble itself. If this option isn't practical, apply some Chalk Paint on a poster board so you can get accustomed to its texture. It may be thicker than other paints you're used to, which allows it to cover the marble with ease.
Lay a drop cloth or old blanket around your marble painting project. Protect your marble surface by circling it with painter's tape.
Sand the marble with a fine-grit sandpaper only if it is glossy. This is a subjective measure, so if your marble is dull and worn, it probably won't need to be scuffed up before painting.
Dust the marble surface to remove dust. Wipe it down with a damp cloth and let it dry. Wipe it again with a microfiber cloth, which picks up and holds dust, right before you're ready to paint.
Apply a thin coat of Chalk Paint to the marble, keeping a wet edge. Let the paint dry for about 48 hours -- longer if it is cold or if there is a lot of humidity in the air. Chalk Paint's longer-than-usual drying time will give you time to decide whether to apply a second coat.