This is an easy, fluid technique to build up lots of texture underneath a painting. This is one of the biggest pieces I’ve done: 20 x20.
Begin with covering the board/canvas in several lighter and darker color patches. When that is dry, cover it all with random brushstrokes of GAC 100. When that is dry, cover the color patches with a light layer of white.
You can apply fabric or tissue paper, under paint to add texture. From here, when an area for a figure begins to “reveal” itself, enjoying shaping it out.