I have two entries for this challenge. I have to say the first time I attempted this I used Blister powder to whip up some watercolor and it did not have the desired results. Then I used my trusty Kuretake Watercolors and some tissue paper and it worked great.
Basically you paint some colors onto your watercolor paper and while wet you take crinkled tissue wrapping paper and lay it down onto the wet watercolor. I waited 25 minutes and then removed the paper....voila!
This is a Technique Junkies stamp set and a sun from parts unknown.