@Shawn R. L.
Allegedly, Rubbing alcohol (Isopropyl?) Is good for thinning down tamiya paints. It\'s cheaper than the tamiya thinner, and tamiya paints have on the side: Warning: Contains Isopropyl and Glycol ethers.
Since I only use tamiya smoke and transparent orange, (hats off to jakob nielsen for that one) I\'m just getting by on tamiya thinner, and water. You get a much flatter finish if you thin it down with water, but it acts a little bit odd.