I draw everything on pain tool sai. And one of my old friends showed me a bunch of thing you can do on it. One of them being able to make things look like they are glowing!
First yah got your image:
Then you make a new layer at the tippy top and change the mode to luminosity:
Boom there you go. I usually go with a lighter color from the base eye color and I use the air brush tool. It’s really that simple.