Here is my completed LO using the picture I did this technique with!
What we are going to do:
Just start out by applying your masking tape in any way you want, the more oddly you apply it the more appeal it has when painted! It's all about what you think looks awesome! Once you get the entire piece of cardstock covered, then paint away! After I painted mine I went back over it with a baby wipe to give it more of an uneven look, but that is completely on the eye of the beholder :-)