Last week in Wednesday's Watercolor class, we played with the plastic wrap technique, laying on our paint thickly and putting crumpled up plastic wrap, then letting it dry. It's a matter of the thickness of paint, putting on the wrap at the right time, and letting the paint dry thoroughly.
Daniel Smith's Lunar Blue and Lunar Red Rock are excellent paints for this because they granulate so well, adding that much more texture. I did add some Phthalo Blue and Quinacridone Burnt Orange as well.
Before we actually did our painting, we practiced, creating small reference paintings for later reference.