We used coated paper 28 lb bond paper, watercolours and plastic wrap!! We started with a letter sized piece of paper, covered it with water using a foam brush, added several colours of watercolour over that and while everything was still wet we covered the whole surface with a piece of plastic wrap which we manipulated with our fingers to create a lot of wrinkles. It is best not to mix the colours too much and to have enough paint to give you vibrant colours in your finished paper. The larger sheets were trimmed to yield two 5" x 8" sheets which we will use in the "Line a Day" journals we are creating!!
I have used this technique very successfully with acrylic inks and acrylic paints as well. You can pretty much use what you have. Have also used a variety of papers - watercolour paper, cardstock and bond - again, use what you have.