If you have ever avoided painting rocks because they seem to be difficult, you are not alone. The trick is to simplify, they are only made up of basic shapes and are usually not alone. Don't see them as something that must have every detail painted in, see them as basic shapes grouped together. See how the light hits them and the color that is reflected on them from what is around them, be that another color rock, trees, grass...anything. Look at the planes, angles and shape that make up that rock, boulder or group of rocks. Start with simple suggested placements of lines and put down what you SEE and not what you THINK you see. Plus, enjoy, no one has to see your finished piece and you won't be out anything but some time and paper. Whether a digital or traditional artist you will have gained experienced, enjoyed nature in some way and spent time doing what you love.