For those who haven't seen it yet [link] I finally took the time to make a tutorial about how I make my jack charms, made of polymer clay (needs to be baked).
I used here glowing in the dark clay.
My english is not good enough to explain every step, but I think the pictures are clear enough to understand how I worked.
If you follow this tuto, I'd be very pleased to see your results!
Background pictures -> [link]