Not wanting to wear a zentai under my clothing all of the time, I found other ways to darken the skull's eyesockets. Goodwill sold cheap black tights during the Halloween season of this year, so I picked up and disassembled a pair.
To hold the tights' black gauze in place, I liberally applied sewing pins.
Glue choice was much more difficult. Super glue is expensive, dries quickly, and doesn't form an effective bond between fabric and spraypaint. Cyanoacrylate emits noxious fumes as it dries, and you don't want those fumes anywhere near your eyes. Don't apply superglue to a project within 24 hours before you'll wear it. I finished off the gluing with Gorilla Glue.