Many transient gene expression (TGE) methods produce insufficient protein quantities for full use within biotherapeutic and vaccine development pipelines. MaxCyte’s proprietary flow electroporation provides a universal means of highly efficient TGE for the rapid production of large-scale quantities of proteins, antibodies, antibody-like molecules, virus-like particles (VLPs), and vaccines. In addition, the platform can be used for generation of stable pools and stable cell lines that can greatly streamline biotherapeutic and vaccine development. Flow electroporation (co)transfects a wide range of cells, including mammalian and insect cells, with DNA and RNA and combines superior performance, broad applicability, and ease of use with the capacity to transfect up to 2E11 cells in under 30 minutes. This technical note reviews the key features of MaxCyte transfection, including cell type flexibility, scalability, consistency, and high-yield protein production that makes this an ideal TGE platform for use in early-phase candidate identification as well as for generating the gram-level antibody quantities needed for late-stage pharmacolgy formulation, stability, and process and purification development. Case studies are presented for gram-scale IgG production in CHO cells, diabody production, and insect cell VLP production. Comparisons with baculovirus expression and lipid-based transfections are shown.