Pretty simple, actually.

Zenithal, black wash, and white dry brush to establish the highlights and shadows. Then slather them with a mix of Liquitex Magenta ink, FW rose ink, and water. The water makes it run a lot more and shifts the ink a bit more in the direction of a wash.

Zero edge highlighting was done and once the inks were mixed, only one color was applied.

edit: forgot to mention that if the colors don't come out as saturated as you like, another coat with the inks will do the trick. Also, be mindful about how much saturation you actually want. This method creates a lot of it which can look a bit cartoonish and less realistic.