In this tutorial you can follow along as I create a beautiful portrait of a child done in oils using traditional painting techniques.
Gesso is a quick drying acrylic paint that is used to prime what ever surface you choose to paint on. As it drys it shrinks, so by priming both sides of a rigid surface like Masonite it prevents warping. I apply a minimum of three coats alternating the direction of brush strokes by 90 degrees between each coat.
After the gesso has fully dried I sand the surface with fine sand paper to get a smooth surface. While some sanding is necessary how smooth you sand it is a matter of personal preference.
Many painters like to lightly seal the under drawing with a fixative before they start painting. If I were starting immediately with color, I might be tempted to set the drawing to prevent the charcoal from muddying the pigments. Fortunately I will not be laying color in until later in the process and I prefer to have the drawing blend into the initial under painting.