For best results when applying gesso, keep the consistency slightly stiff in the first layer. Start by brushing an even coat of gesso on your surface, moving in one direction. When the gesso dries, sand it lightly with fine sandpaper. Add a second coat of gesso perpendicular to the first, then sand lightly again. If you decide a third coat of gesso is necessary, try a slightly thinner consistency: three parts gesso to one part water. When it dries, sand once more. This procedure should give you a dense, even gesso ground that provides a smooth foundation for painting.
John Kevin Flynn is director of the J.K. Flynn Co., an art restoration and appraisal firm in Brooklyn, New York.