The state of a perovskite precursor ink is set by how its solvents coordinate the precursors, yet the roles of individual solvents in green binary mixtures remain poorly understood. Here we examine how 2-methoxyethanol (2Me) and 1,3-dimethyl-2-imidazolidinone (DMI) share the solvation of the four precursor components of a formamidinium–methylammonium (FA–MA) lead iodide–bromide ink: PbI₂, PbBr₂, FAI and MABr. Cluster–continuum DFT calculations (r²SCAN-3c/SMD) of the exchange of 2Me for DMI in the first solvation shell show that PbI₂ prefers DMI, whereas PbBr₂, FAI and MABr prefer 2Me (+4.7, +4.2 and +8.4 kJ mol⁻¹ per DMI); in FAI and MABr, 2Me donates O–H···X⁻ hydrogen bonds to the halide anion. A thermodynamic model built on these energies points to 2Me-rich mixtures (about 10–20 vol% DMI) as the best compromise. All 2Me/DMI mixtures wet the polymer PTAA, with the contact angle falling from 24.7° (2Me) to 13.3° (DMI). Without an anti-solvent (gas quenching only), the 2Me:DMI ink gives on PTAA a film with larger and more uniform grains than the DMF:DMSO ink, with the same absorption onset (776 nm). Together with literature data on blade-coated films and modules, these results support 2Me/DMI as a solvent system for anti-solvent-free, large-area processing of FA–MA perovskites.