How to Paint Faux Marble
Prepping the Piece
The first step is to thoroughly sand the countertop and apply an overnight coat of primer. After the first coat of paint is added, smaller sized shapes should be marked out using masking tape. These will then be painted over with lighter and medium matching shades of the base, dark color.
Once all the different marked out areas are taped down, it's time to paint these them. Starting from the center of each taped out area, the lighter shade of matching paint color is applied first, using short punch-like strokes of the paint brush. To achieve a true marbling effect, small taps of the paint brush are preferable to broad, standard brush strokes. For each taped out area, the idea is to start from the center with the lightest color shade first, then repeat the process with a darker medium version of the base color. As these additional shades are applied, they blend into the base to create a marbling effect.
There is one more critical step. Once the taped out areas have been painted, it is time to add in white marble-like veins. For this final effect, a separate artist's paint brush and white paint is required. Some veins can be thick, others can be thin. There is also the option of interrupting the tracing of a marble vein so as to create a sectioned effect. Given the heavy use of bathroom and kitchen countertops, several separate coats of polyurethane are recommended.
Faux Painting Inspiration
Although the innate nature of the marbling effect is forgiving to mistakes and irregularities, it is always preferable to find a book that features examples of the effect being created. Amazon.com features a number of great sourcebooks such as The Art of Faux by Pierre Finklestein. Simply search for "faux marbling" or "faux marble."