This chapter delves into the flexible, multi-sited methodology designed to study mobile and irregularized populations under shifting constraints. Fieldwork unfolded in three phases (2021–2025), combining team ethnography in high-risk urban settings (Tijuana), collaborative work in Tapachula with legal–anthropological perspectives and a local researcher, and follow-ups in the U.S. and across changing routes, including attempts to track flows through Nicaragua amid sudden policy shifts. Methods integrated in-depth interviews, participant observation, and sustained digital ethnography (WhatsApp calls, voice notes, photo exchange), enabling longitudinal engagement as interlocutors moved to Mexico City, the U.S. or Canada. The approach foregrounded security planning, opportunistic sampling, and iterative site selection in response to COVID-19 disruptions, violence, and route volatility. Ethics and reflexivity were operationalized through informed consent, anonymity, data protection, and continuous attention to power asymmetries and responsibilities beyond extraction. Team-based practices functioned both as a safety strategy and an analytical asset, producing multiply-positioned accounts that captured gendered, racialized, and bureaucratically mediated experiences of “being in transit.” Overall, the chapter argues for methodological adaptability and ethical accountability as core requirements for contemporary migration research.