I think these are my grungiest creations ever.
I just spent ages layering acrylic paint until I just reached the point where I liked how it looked. Again, as has happened several times now, it is only when I cut it up that it takes on a whole new look, and each piece is quite different.
I simply Gesso'd a piece of 300gsm card and began applying the paint, initially with my fingers, I find this quicker and easier to blend the paint. It was only later that I used a bristle fan brush for the sweeps of white and black paint.