In Rains et al. 2021 (arXiv:2102.08133) we conducted a medium resolution optical (3,500 < λ < 7,000 Å) spectroscopic survey of 92 cool (3,000 ≲ Teff ≲ 4,500 K) southern TESS candidate planet hosts and 136 cool dwarf standards using WiFeS on the ANU 2.3 m Telescope. As part of our model-based fitting methodology, we conducted an investigation into MARCS model atmospheres and found they systematically overestimate flux the cooler the star and bluer the wavelength. In addition, we developed an updated photometric [Fe/H] calibration with Gaia+2MASS photometry for isolated main sequence stars precise to ±0.19 dex. This was built upon a calibration sample of 69 cool dwarfs in binary systems with a hotter FGK companion, valid from super-solar to metal poor, and over 1.51 < Gaia BP‒RP < 3.3.