When painting miniatures (or ponies) with acrylic paint, yes, you definitely need to water it down! I found success with thinned acrylic at the consistency of milk. I used a large, soft-bristled brush to lay on the body colour, and teeny tiny brushes to do eyes and symbols. It will take more than one coat for complete coverage - more coats for light paint colours, and fewer coats for dark. Good luck!