I'm painting over an old painting, so first I sand the surface of the canvas, wipe off, then rub over it with a rag saturated with linseed oil/mineral spirit mix. I painted my initial layout using thinned down ultramarine and a #6 bristle round brush. This is the only time I really ever use a round brush! Mixing the values I want and not worrying too much about getting the exact color, I lay down paint in big shapes. Ok, that's all the time I have today!