Use only one size and type of brush rather than a range of brushes. That way you get to know exactly what it’ll do and how to get the same effects or results repeatedly. It becomes intuitive, instinctive, rather than something you have to think about while using it. (Katie uses a Raphael Series 8404 #2 for almost everything, including detailed work, and a Raphael Series 8404 #4 for large washes.)