If you are only working with up to med format negs you could devise an inexpensive fluid mount experiment using appropriate Gepe glass "slide" mounts. But after I'm done using cleaner and a no-mar
scrubber on my enlarger glass, I rinse it off in running water (I have soft water, but if you don't, you
should used distilled), then blow any remaining water droplets off with a nozzle from my compressed
air line. There are various ways to clean glass, and probably a number of past posts on this subject.
I always mount the negs in a sandwich of glass on both sides, because it is the only reliable way to
get consistently sharp prints; but some people obviously prefer other methods.