I encourage my homeschooled children to sketch and doodle (see example of doodling during sermons) about their interest to engage themselves more fully with their material. Doodling is a great way to learn how to abstract out the basics of what they have learned when words can only slow you down. They use it mainly for personal exploration of the subject on hand and is not meant for sharing with the world. Recently, for example, my metals-focused son enjoyed sketching several versions of the Bowie knife to highlight the various functional elements of the blade. My other son, who is focused on the history of coins of money, sketched out several pages of the development of early banking with goldsmiths in England.