I am working on my Heroclix demons. None of them started as demons, some were super heroes and some were super villains. I did not strip them of the original paint. I did prime them with a light colored grey primer. All of them were removed from their original bases.
They were then repainted with a hull red spray paint, from Tamiya. Once dry I painted them again with four different gloss red colors. One of them I used for their "clothing" and the other three were for dry brushing the "skin." Those with "fire" on them got their fire painted yellow, with red highlights to the fire.