What paint to use for Shell Tops?

[Mermaid Miel]

I have two gorgeous LionsPaw Shells for a Shell Bra, and I would love to decorate them like Traci Hines' or EmilyAngelfish's shells....
but what type of paint do you use?
Are there any sealents or varnish you would recommend?
This is for a Wet Top... did you have any problems/fading with your shell top after a dip?

[Mermaid Saphira]

I used acryllic then coated the shells with rust away or whatever its called :)