What type of rice and which grain-size as flour is best for which use case?
I have got a grain mill and am going to do lots of gluten-free recipes with rice flour. From cake, via pudding, to mochi (Japanese dessert)... at some point in time I want to have them done all, at least once, and my question is how fine should I grind the rice and which type of rice should I use for what?
For mochi one needs glutinous short-grain rice, for sushi sushi rice. With bread and baked goods everybody knows which grain size of wheat flour one should use. But is it the same grain size for rice flour?
There are a few good rules of thumb to decide what grain size to choose.
The best recipes will specify what flour type to use. Go with the type required by the recipe. Note that, if a recipe is highly specific in the very exact flour type (and even brand) needed, and you don't have reasons to suspect a purely marketing purpose, it may be not a good choice for your homemade flour. For example, I have a book of gluten-free bread recipes, where the authors explicitly state that rice flour from Asian markets won't work, because it is not sufficiently consistent from batch to batch; with homemade flour, you will get even less consistency.
You can guess at the type of flour by the recipe's origin. Asian recipes (or recipes for Asian dishes, even if coming from Western authors) are likely to be written for superfine flour, and you also have to pay attention if they specify glutinous or nonglutinous rice. In Germany, the predominant rice flour is "grippy" - it has a larger grain size, but not large enough to be legally classified as semolina - and wholegrain. I have had Italian rice flour in a similar size. In other European countries, it even happens that products labelled as "flour" turn out to be coarse enough to only be usable for gruel, with grains on a millimeter scale. My understanding is that American rice flour is also coarse like in Germany, but frequently white.
You can also try to guess by the recipe directions. If the recipe directs you to mix the flour with sugar or cold liquid before adding it to other products (especially to something hot, as in puddings or ice cream bases), then it presumes finely milled flour. If you have to sieve the flour, it is likely to be fine. If it has resting times, it is more likely to be written for coarser flour, which benefits from extra time to hydrate properly.
If your dish is a gluten-free version of something typically made with wheat, it is a good guess to start with the size required for the wheat dish. A pasta can gain a more interesting bite if made with coarser grain size, while a dainty pastry is better made with fine flour.
There are a few edge cases. Off the top of my head, if you have a cake batter that is more on the liquid side, or if it is very fluffy (e.g. a genoise), don't use coarsely ground flour - it will sink during the baking, building a stodgy layer on the bottom.
If none of the above applies, use whichever flour gives the effect you prefer. Many dish types will work with both, for example you can make frying batter with any size of flour grains, or even with semolina. Decide what you want, and use that.
The suggestions are ordered roughly by order of application - if you can use one that is higher in the list, you don't typically need to worry for those listed further down.