This study investigates how elementary teachers’ understanding of scientific models (Epistemic Resources for Modeling; ERM) and their instructional practices (Pedagogical Resources for Teaching; PRT) are enacted from a resource-based perspective. Lesson videos and interviews from five teachers were analyzed using Rodriguez’s framework of resource grain size. The findings indicate that ERM and PRT often appeared in overlapping structures—ERM elements (distributed or conceptual) were embedded within frame-level PRT. These resources were selectively activated depending on instructional goals such as concept clarification, inducing cognitive conflict, presenting alternative models, and expanding ideas. The grain size and combination of resources varied with the teacher’s purpose and lesson flow. This suggests that teachers’ model-related knowledge is not fixed but dynamically constructed from epistemic resources. The study provides a new lens to analyze teacher thinking in modeling instruction and informs directions for science teacher education.