We needed to loosen up in my adult watercolor class so we did some very loose sunflower under paintings on quarter sheet watercolor paper. Then took some tissue paper and 50% water/mod podge mixture to glue the tissue (some use rice paper) paper down controlling the wrinkles. Then painted over the dried tissue paper with washes and color letting drips and the color settle where it wanted to. It is hard to let go sometimes and just let it happen. We were feeling the sunflowers, not painting details. Does that make sense? A good lesson.
Below is the Heinz factory in Pittsburgh that I used this technique on from a while ago.