I use to make my own when I made my Glow jigs. Glow Powder and Clear Powder paint, but have to be very careful how much Glow powder you put in the clear paint and if my memory serves me it's something like 20% max. I also use to coat over with Sally Henson's Hard as Nails to make the coating feel smooth because it's a rough feeling until you go that. Still this heads don't glow near as bright as my bodies do, lol!
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Notice I didn't even turn off the overhead light and just held them under my desk just barely out of the light.