The next step was to crumple up the fabric to make "cracks".
After the fabric was smoothed out again, it was sprayed with black fabric dye.
The dye was allowed to dry thoroughly, then was ironed between sheets of newspaper to remove the wax.
It took many layers of paper. At first, a LOT of wax came off. Here is what it looked like after repeated ironing between newspaper:
A couple of the colors blurred a bit with ironing. Overall, I am happy with the effect. Next will come quilting and embellishment. The original source suggested outlining with black permanent markers to emphasize shapes. I think that stitching will accomplish the same.