Place something between the shirt layers to catch all the paint that may bleed through. I used a cereal box cut down.
I used gold fabric paint and had to do two coats. Let dry a bit, and remove freezer paper while paint is still a bit wet. Otherwise it gets stuck down with the paint. Let dry 24 hours and heat set with a DRY iron and you are ready to go!
You can see on my sample, I hurried through the process and some of the paint got under the 'stencil'.
Give it a try, it's really easy!