I finally got a chance to try using both saran wrap and wax paper to create textured effects. I used each technique to create backgrounds.
I tried it a second time on a similar painting in a Strathmore watercolor 140 lb paper journal. This time I quickly applied a very wet wash using my flat Niji waterbrush and it turned out much better (see below).
I then used wax paper on a mixed color background also on the Strathmore watercolor 140 lb paper. After doing a quick pencil sketch, I wet the paper using my spray bottle. Then I dropped in a few different colors and let them run together. Before they dried I added the wax paper and squished it around. Once the background was dry I painted the squash, and added a shadow to ground it to the paper.
As you can see in the below finished journal entries, the effects were very similar. This technique is very nice for adding some background interest without distracting from the central image.