If you haven’t learned Photoshop yet, what are you waiting for? It’s a fabulous tool to enhance your renderings, both hand and digital. You can also build an entourage library with it. Import digital photos into it, cut them out, and then scale/place them into your renderings. You can alter their clothing colors or turn them into gray figures to better match the space.
Students can buy Photoshop at their college bookstore for about $175 and the whole Creative Suite for about $400. If you want free, the open source GIMP program, which operates similarly to Photoshop, can be downloaded here.