You can pull out grasses, tree trunks, etc. by dragging a flat object (credit card edge, chiseled end of brush handle, etc.) to make grasses or tree trunks, and the amount of moisture in the area of the painting will determine if the scrapings pull back to a lighter paper (done when the area has lost its shine) or fill back in with the surrounding moist paint and get darker (if done when it’s wet).
This was a scene where we had instruction to put in the background sky, trees, house and then do grasses in front. I worked on it a bit at home as well.