Expressive digital drawing requires nuanced motor control, subtle variations in pressure, velocity, and rhythm that convey affect and style. While experts develop this embodied fluency through years of practice, novices struggle to produce marks that match their intentions, creating a gap between vision and execution. We propose motor-mediated creativity: treating motor training as integral to digital expression. Our system, {\system}, instantiates this through structured practice of expressive primitives, expert-referenced feedback, and ideation prompts that encourage exploration. We report a two-stage investigation. A formative study characterized: (a) novice challenges in motor fluency, (b) examined how different feedback types, including corrective feedback, helped participants understand their mistakes, (c) how prompts, generic or embodied, support engagement with abstract expressive content. A controlled evaluation then linked fluency gains to subjective and expert ratings of expressiveness. Together, our findings show that scaffolding motor skills is a viable strategy for enhancing expressive agency in digital drawing.
ACM CHI Conference on Human Factors in Computing Systems