We report from a research-based professional development program - the fellowship program - aimed at scaling digital design literacy in Danish K-9 education. The fellowship program was designed to engage with experienced K-9 teachers to provide them with the knowledge, experience and resources needed to further develop digital design literacy in their local school environment and to create networks for continuous exchange between researchers, educators of teachers and in-service teachers. In this paper we present the motivation, strategy, partnerships and execution of the fellowship program and report from survey results assessing participants gains and learning outcomes. We position the fellowship program within the broader discourse of leveraging teacher training in computing education and digital design literacy. We suggest that the fellowship format has a number of qualities that make it a potentially valuable addition to established teacher training initiatives. This includes the establishment of feedback loops and networks between researchers and practitioners, scaling through local peer-to-peer training, a modular and agile setup and the collaboration between educators of teachers and in-service teachers.