... I thought I could just cover the grill and the back of the capsule with some kind of tape to protect it from the paint, but...Vapor from solvents – either from paint or from cleaning attempts - dilute the diaphragm material and thus kill the capsule.
Even small amounts have this effect, as the diaphragm is that thin.
Just as a warning if one has such an idea.
Only dry cleaning should be done on a condenser mic.