Layering can include drawing on your painted surfaces using drawing materials including oil pastels and oil sticks. The drawn elements may contract with the painted ground of complete and compliment it. The drawn lines may be transparent, light and delicate with the ground dominating, or thick and heavy like the kind made using oil stick colors.
Below: almost none of the acrylic painted ground is visible under the oil paint and oil stick drawing
Below, the painted surface pattern before drawing on it with oil pastel
then I drew on this pattern painted surface with oil pastels, intending to keep the lines less intense and allowing the ground to dominate