Staff facilitators in museums and science centers are a critical but often overlooked component of the visitor experience. Despite assertions about the important role they play in visitor learning, there continues to be almost no research to understand staff facilitation in these settings or identify effective practices. To address these gaps, we conducted a design-based research study to describe the work of experienced museum educators and iteratively refine a model of staff facilitation to support family learning at interactive math exhibits developed through a prior project. The resulting