I really want to give Green Stuff World paint a go. It is affordable and they have tons of different colors, metal finishes, inks, and paints they call "filters."

The paints are acrylic.

I looked all over their website and I can't find what type of acrylic they are, or what I can think them with. 

I want to try these paints, but I'd hate to buy GSW Thinner when I likely have what I need already.

So what can I use to thin these paints?