I used this base to get his design up!
Speaking of, his original design is here, with some minor changes from yours truly.

I'll draw him myself eventually but I'm stuck working on my sona's ref and I'm super lazy

For the glowy bits, I make a new layer on top of everything and draw with a soft brush on top of the glow parts. I use whatever color they are - so the antlers and tootsies are light green and the spots on his back are off-white. Then I set that layer to vivid light. This is just how I do it, and I'm just typing this out so 1. I don't forget how I did this and 2. In case I commission someone to draw him. I don't want to confuse anyone.

Not yet, anyway.