It's really up to you what you want to include in your brain dump. Whatever you think will help you most with the exam. A lot of people create a chart of the Knowledge Areas and Process groups, and then write down all the formulas, and find this sufficient to get through the exam. If there are any other areas you think you'll need help remembering, just add them to your brain dump, being mindful that the more you put in your brain dump, the more time it will take away from your actual exam.