I use this stuff. Comes in a bottle with a dropper tip, kind neat (put the red plug back in after you use it, though). It works great and doesn't stink much, so my wife doesn't complain (much)...(about the paint smell, at least). I will observe that you don't need much for the MM acrylics, you can almost shoot them right out of the jar. If you get too much thinner, the coverage of the paint really drops off and you'll have to shoot another coat.