A couple guys in my model club are using Mr Leveling Thinner to thin Testors enamel paints.
I honestly don't know how that can work because Mr Leveling Thinner is really supposed to be for lacquer paints. But they use it and love it.
And on a side note. I would also suggest going online and buying Tamiya X and XF series acrylic paints. They dry so much faster than Testors paints. They airbrush well if you plan to do any airbrushing. They are really great paints.