Another technique from Collage Discovery Workshop-Expect the Unexptected by Claudine Hellmuth. This one is the Plastic Wrap Crinkle technique. Done on canvas pad with acrylic paints. I used Golden's paints for these samples but you can use what you have handy.
I used two colors of watered down paint (consistency of watercolor) in puddles, mixing the two colors in spots. Then put a piece of plastic wrap over the paint and smooshed it around with my fingers. This one has to be set aside to dry. If you use the heat gun you'll melt the plastic wrap. When dry remove the plastic.