Can this be used to enhance regular or traditional baked products?

I’d like to make a coconut flour sourdough and wonder if you would have suggestions for that? It’s non-grain, gluten free and I had some last summer but the baker wouldn’t give away her secret! In fact, she claimed it only had water, salt and coconut flour in it (natural yeast from the air)…but it was fluffy and delicious…so I am not sure there isn’t something like Expandex involved.

Hi! I have a couple questions. I generally use 1/3 starch (usually a tapioca/potato starch blend) and 2/3 whole grain flour (a mix of a few of the following: millet, sorghum, teff, cassava, buckwheat, etc) when making gluten free breads and treats. I don’t bake with rice flour at home because I have small children and worry about arsenic loads in gluten free diets. Should I substitute expandex for part of the starch so that expandex accounts for about 10% of total flour by weight but keeping starches around 30% overall? Or add it in addition to the starch so that the overall starch component is roughly 40%? Also, do I need to increase liquid when using expandex? Thank you!