Facilitating dialogic discussions in English classrooms is a key component of fostering student learning and working toward educational equity. Orchestrating high quality text-based discussions requires attending to the unique situations that arise when particular students grapple with complex ideas in rich texts. It also requires making quick and efficient decisions based on familiar situations that commonly arise during discussions. Preparing teachers for such sophisticated practice is challenging. This study explores a practice-based approach to learning to facilitate dialogically oriented text-based discussions. Through an exploration of rehearsals of discussion facilitation in a summer professional development, we identify two types of framing for coaching moments -- ones that attend to generalities of discussion and ones that attend to novelty in discussion. We find that attention to generalities helps develop teachers' efficiency in facilitation, while attention to novelty helps develop an ability to innovate in response to students' contributions. Together these two aspects build toward adaptive expertise (Hatano & Inagaki, 1986) in the facilitation of discussions. We consider how English teacher educators might balance a focus on efficiency with a focus on innovation in light of the value of adaptive expertise supporting teachers' implementation of dialogic discussions.