The gluten flour mix that I use most often comes from Gluten-Free Baking Classics by Annalise Roberts. It calls for "extra fine" brown rice flour that I order online from Authentic Foods since my local store doesn't carry it. You can also buy Annalise's flour mix pre-made by Authentic Foods if you don't want to mix your own. I've been using the extra fine brown rice flour for about 18 months and the thing I love most about it is that the gritty texture I once found in my baked goods is no longer present. Give it a try and let me know what you think.
Gluten Free Flour Mix
6 cups brown rice flour (extra finely ground)
2 cups potato starch (not potato flour)
1 cup tapioca flour
Mix together in an airtight container. Makes 9 cups.