Glow eyes is pretty easy. You’d need to paint that black a lighter color, like light grey or white. Then just start building up the fluorescent color, more layers in the middle, less on the outside. Can add white to is as you keep building the inside. Once it’s nice and bright like you want, add some pure white in the center.
Do some lighter layers on places like the bottom of his eyebrow, the tops of his nostril, and a bit on the top of his cheek bones near the eye. Practice the layers on a piece of card stock maybe if you’re nervous. The pure white in the middle makes it really pop.
A closeup of some flouro green glow I did in the past using the technique above.