I'm an oil painter. I am unsure, however, how oil paint will respond to being warmed and cooled over and over and over, so I'm using acrylics in this project. I chose the Winsor & Newton Professional line, because they are good quality for the price, and they don't shift color too badly as they dry.

I got an assortment of thermochromic pigment powders from Adafruit. They come in little packets, and the powder is super finely ground. In my first tries, I mixed the powder with transparent medium (essentially a thin, colorless paint) and I just did not like the results. It was hard to apply and came out too much like a glaze. This time, I've tried mixing the powders with white paint. I won't get as deep a color this way, but the body of the paint is better and easier to use and mix with.

If this plan generally works, I may try getting some transparent gel medium, which has a thicker body than the stuff I used before. I would like to be able to get rich color, and I'm concerned that using the white paint will keep things too pastel.  

The crux of the success of this project - success in an artistic sense, anyway - will be how well I can make interesting color mixing choices. It's not anything I can just figure out in my head, it's going to take a bunch of experimentation time and effort. So I should probably stop typing and get back to the easel.