Get yourself a bottle of "Isodry" or any other isopropyl alcohol based
"dry gas".
Holding your fingers over the ports in the bottom fill the reservoir approximatly 1/2 full, install the cap and shake the hell out of it.
Dumping the alcohol when it gets dirty
repeat as necissary.
then blow it out with compressed air (or allow to air dry)
before installing it.
If the alcohol fails to remove the "spooge" then you can try to clean
the reservoir with aerosol brake cleaning solvent
DO NOT use the "non-chlorinated" type, specifically look for brake parts cleaner
that is made from Tetrachloroethan or perchloroethane.
Rinse that out with the isopropyl once you have it clean enough.
AD