I checked with our thin section lab operator and they use a 50/50 mix of ethylene glycol and pure ethanol, a formulation based on... some ancient thing they read. Seems to work, but we work more with hygroscopic than water-soluble materials. They said they weren't sure whether or not changing the ratio would have any effect on anything, as they understand it the ethylene glycol is there to help slow down the evaporation of the ethanol.
Back in school we used kerosene with grit in Vibromet polishers on metal samples, but I think kerosene has fallen out of favor as a polishing solvent.
edit: I know the user titles on the forum are just automatically generated based on post count, but we should all just take a nerd moment to appreciate that this thread was started by "A lerner, Student"