For this technique you use watercolors and watercolor paper. Tape down the watercolor paper to keep it from warping. If you have a planned use for your background, start with a larger size sheet of watercolor paper, as the area under the tape will stay white. For my first sample, I started with a graded wash of blue watercolor.
While the paint was still wet, covered with wrinkled plastic wrap and waited for it to dry.
Here's how it looks:
Julia also suggests trying the technique with several colors at one time. I choose yellow, blue and purple. Covered with wrinkle plastic wrap and let it dry.
Next I did of wash of two shades of blue watercolors and sprinkled on some Perfect Pearls (instead of blending in the Perfect Pearls with water), covered in wrinkled plastic wrap and let dry.
The shimmer shows up better in "real life":