Brain sketching is a technique where individuals quickly sketch out their initial ideas on paper in silence to leverage the creative parts of the brain associated with images rather than words. This allows introverted people space to generate ideas without interruption and recognizes that more ideas are created individually than in groups. The key steps are to consider a creative question, sketch 6 initial ideas within 5-10 minutes using minimal words, and then share the sketches with a team to build upon the initial ideas.