The field of language documentation continues to grow, but an historic split between sign language documentation and spoken language documentation persists. In order to fully understand the linguistic context within a community, it can be necessary to overcome this split by designing language documentation projects to address threatened and unreported languages across modalities. Additionally, these two subfields can lend insights to the other both with respect to the analysis of individual languages and best practices for language documentation. Drawing on an example of parallel projects to document and describe a spoken language and signed language of Papua New Guinea, this paper provides recommendations for researchers in similar situations. Benefits and practicalities of team-based research and extensive use of video recordings are discussed as essential for creating holistic language documentation with outcomes which are useful and appropriate for an entire community. Because many endangered and minority spoken languages are used in areas where there is little existing knowledge and documentation of signed languages, this situation is unlikely to be uncommon and this type of work has potential to further sign language linguistics, typology, and best practices for language documentation across modalities.