Get a corona mill. Amaranth and teff are tiny--think grains of sand. Quinoa and millet are also quite small. Chestnuts are big and would be fine in a barley crusher.
: Beet-Buckwheat RIS, Oatmeal Cherry Stout, Galaxy-Hopped Bochet, Multi-Grain Winter Wit, Oat-Pecan APA, Sorachi-Chamomile Blonde, Quinoa IPA, Black IPA, Nelson Agave Cream Ale, Buckwheat Stout
: Chestnut Saison
: Mosaic IIPA, White IPA
: Chestnut Stout, some kind of amber
All gluten-free, all the time!
Check out my gluten-free brewing blog, beyondbarley.blogspot.com