I doodle on dry erase to. Mostly just for fun and to remember designs I want to try on quilts. I like doodling in different sizes on purpose, because it's much more natural for me to doodle small, but I have to almost 'force' myself to make the shapes real large. I actually have to think about making it bigger. As I doodle, the shapes start leaning and shrinking naturally.
SketchBook is fun too...so is scrap paper...