I use several different flours, but Bette Hagman's Featherlight Mix is the one I use the most. I mix up a 5 gallon bucket at a time. I buy my flours & starches at Honeyville Grain in Salt Lake in 50 lb bags and store the extra in 5 gallon buckets as well.
1 cup Rice Flour
1 cup Cornstarch
1 cup Tapioca Starch
1 Tbsp Potato Flour (not potato starch)
For a 5 gallon bucket I 5 times the above recipe in a big bowl then dump into the bucket. I do that 4-5 times until the bucket is full. I find it easier to mix when doing it in smaller amounts.