Apply a coat of water based white primer. Use a medium size disposable brush. Since there is no grain, and the resin does not absorb oils, as wood does, water based primer works better. Allow this to set for about two hours before proceeding.
Choose three colors of stain from a finished sample of actual hardwood in the color you want to match. Choose the lightest color, the darkest color and the predominant color, or the color that show up most. Use stain chip samples to compare the colors to the wood sample and purchase the best matches in a water based, gel-type stain.
Brush on a coat of the medium or predominant color. Use a fine bristle medium brush. Cover the entire corbel, working the stain around the edges to the cover the outside edge of the back as well. This helps to seal the face and ensure that none of the white primer or resin will show once your corbel is mounted.
Apply the darker color next, while the base is still wet. Use an art brush, working this shadow color into the details of the corbel. Use a fan brush or other thinly bristled art brush to streak a little of the dark color along the other faces of the corbel, in the direction that wood grain would run if the corbel were wood. Allow the corbel to dry completely.
Apply the lighter color to any area that is raised, or where light would normally cause a highlight. The rule of thumb is to create a highlight for every shadow. Use a fine point art brush to add thin streaks of light along the edges of the deeper shadows to create even more depth. Use the fan brush to streak a little over the surface of the corbel, in the direction you previously established for the faux grain with the shadow color.
Allow the corbel to dry completely. Brush on a coat of semigloss clear, water-based furniture finish over all of the stained grain. Allow this to dry before mounting the corbels.