Genesis states on their web site that “transparent washes can be achieved by tinting the Thick Medium. Using the Thick Medium gives you a good layer of paint and the transparency that you need". Some doll makers mix a wash by thinning Genesis colors with odorless thinner. Genesis states that "thinning with a small amount of an oil solvent will not permanently thin the paint, as the paint will return to its original state as the solvent evaporates off". Read more about using Genesis products at: http://www.genesisartistcolors.com/instr.html
To use as a blush on the body, apply a bit of the Thick Medium on to a flat glass surface and tint it to the color you desire. Work it to make it soft and buttery. The consistency is soft but thick and transparent. Take a very tiny amount and smear it on the glass palette until it is very thin layer. Then dab a cosmetic sponge into it. You want the sponge to pick up just a tiny bit of it. Apply to you doll using a pouncing motion where you want to add blush to the head and body. Always apply a thin layer, heat set, and then add more until you achieve the depth of color you desire, like painting with china paints.
Be sure to check this blog's INDEX and click on the topic 'Painting" to read more about heat set and acrylic paints.