With Saran wrap the effect will change depending on how long you leave it on the paper. For a subtle textures, take the saran wrap off the paper when it is not completely dry. If you allow it to dry completely the Saran wrap will leave a more geometric pattern.
I have always used Saran wrap for background textures in my Still Life paintings. A color like Raw Sienna used for the background with saran wrap that is lifted off before the paint dries gives the effect of a hand plastered wall, perhaps in Tuscany.
Waxed paper gives a very different textural effect. With waxed paper, do the same procedure, but put something heavy on top to hold the waxed paper down. Try both and see which one you like.
Draw image in pencil on watercolor paper. Wet paper. Flow on your choice of watercolors. Gently press the Saran wrap into wrinkles on the paper. The paint must be wet when you first put the Saran wrap or waxed paper on. I love experimenting and wondered how it would look if I used the Saran wrap on the object (in this case the pear,) not the background, and I am very happy with the way it came out. Please enjoy the video. Let me know how it went for you.