water! there are 2 types of acrylic, the ones in the tube are better quality but more expensive, they can be watered down more than the ready mixed ones in the mini bottles, they usually leave a shine and are splash resistant, but the matt acrylic in the bottles are not, if you do have the tubed paint you can get a clear gloss or matt for acrylics, to seal, but this isn't necasary. It just prolongs the life. You can also design T-Shirts with this paint too, cover with baking paper and on a med setting iron in. I like acrylics as you can use them neat to get the rough oil effect, or really water down to get the water colour effect..good choice!
Acrylic painter. they are the best