Ultrafast coherent multidimensional spectroscopies have become invaluable techniques to interrogate molecular structures, interactions, and dynamics in the condensed phase spanning the THz to x-ray regimes. Spectroscopic studies of increasingly complex chemical and biological systems present many challenges in data collection and, especially, data analysis and interpretation. These challenges include spectral congestion, signal overlap, solvent background, solute-solvent interactions, and the need for high concentrations. In an effort to overcome these challenges, significant recent advances have been made in the collection of ultrafast nonlinear spectra in isolated, gas-phase systems. The low number densities of dilute gas-phase ensembles, however, often prohibits the ability to directly measure light absorption and the emitted nonlinear signal field. Instead, indirect "action" approaches that encode the desired nonlinear signals are required, which present unique technical challenges.