Isopropyl Alcohol is best, RV antifreeze is OK, but it takes more. Compressed air creates a LOT of water condensation. You may try adding an inexpensive, automatic water separator on the output near the Gast pump. If possible, run a loop line to let the air cool and condense the moisture before it enters the separator/ejector.
example...
https://www.youtube.com/watch?v=A8JwN0l-_pA
