There should be a Mr. Thinner of at least one sort. Given how many Mr. products there are, I would not be surprised to see #11 blade-sized bandages marketed as Mr. Kuso.
Science created airplanes and skyscrapers, but it took faith to bring them together.
Denatured alcohol also works to thin Mr. Surfacer for airbrushing. It does evaporate quickly, so mix, load and spray. Clean up as soon as you're done (I just run denatured alcohol through my airbrush afterwards).