NavList:

I know the condensation problem you describe. In my Davis AH, I use old dirty motor oil. It works great. Stays flat in the wind, no condensation,  and dull dark brown reflection reduces the number of sextant filters needed with sun shots.

To avoid a cleanup mess, I  put a sheet of thin kitchen plastic food wrap into tray first. Then add the oil. When done, I pour the oil back into my container and discard the plastic film. No  Davis AH cleanup needed, oil never touches it.

Ed