As promised, here are the "after" pictures from one of my flour paste resist experiments. I soda-soaked the yard of rayon before applying a thin-ish flour paste using a squeeze bottle.
In the detail shot below you can see that there's a halo around the lines. I think that the water in the paste migrated into the fiber and pushed some of the soda ash away from the flour paste. I let the paste dry on the cloth overnight and I think that helped produce good contrast. Cleanup was a lot easier than I thought. After a bit of soaking, most of the paste flaked off. The rest dissolved. After a trip through the washer there's no trace of the flour.