Acrylic Paint and Water Color when mixed, from my experience, make it chunky and runny. if properly mixed and it´s fresh, clean, paint you can but DO NOT use a lot of WaterColor, because it will make the Acrylic Base lose most of its pigment. It can be done, but for it to look good i don´t suggest it. You can do seprate layers for more defined lines and contrast but mixing isn´t suggested.