After watching Jane Dunnewold on a Quilting Arts episode, I decided to try flour paste as a resist. It's easy and it works.
Half flour, half water mixed to a smooth paste is spread on the fabric and allowed to dry. I crinkled it up to get lots of cracks then painted it with black acrylic paint. It needs to be a paint that doesn't have to be heat set. Then it was soaked in a pail of water until the flour was off-lots of rubbing. The water was thrown in the flower bed, so there would be no drainage problems in the bathroom. I'm pleased with the results and happy to work with a non toxic process.