This is just a quick note. When I made amazake for the first time, I followed Makiko Ito's recipe in the Japan Times. After I stirred together cooked rice, water and koji I found that the mix was quite dry. I thought it would be soupy! Checking the amounts three times and looking at several other webpages made me more confident that it should indeed be dry and would become liquid over the course of the fermentation. And it did!
So, if you've mixed together rice, water and koji and it looks like a mound of mushy rice with hard bits in it (the koji grains): this is how it should be. The fermentation will turn it into porridge.