i use model master emamel paints.....which are oil, or petroleum based. with that said, i thin mine with mineral spirits, turpentine, or lacquer thinner.........all of these can be found at the local hardware store or walmart for that matter. i use mm enamels for the majority of my paint jobs. i also use artist oils, which are found in the art section of most walmart stores, and i use these for weathering such as washes and drybrushing.