Underpainting or what they used to call dead coloring paying attention to the line.
Put everything on the canvas in ochre and meanwhile figuring out how to build out different surfaces. In oil I use the mass of the paint to build out rocks, here I want to use transparent glazes because they look more 3d dimensional in acrylics.
It's counter intuitive to use subsurface scattering for rocks but I want to paint jewels encrusted gold rather than dirt and stone.