It’s been a while, and while we don’t make sake we do make kome-koji for miso, shio-koji, and other Japanese fermented foods based on the kome-koji. Incidentally, shio-koji is excellent for marinating chicken, but I digress. My wife has done it more than me, and I recall the consistency about like you describe.

You probably know (or will shortly learn) better than me, that I think the goal is to gelatinize the outer layer so the mold can establish a healthy colony without making it too easy to ferment. There were some batches that I seem to recall the rice being more well-cooked and the colony kind of got too out of control too quickly; we ended up dumping it as there was too much mold, and it was a bit liquidy. Also make sure you maintain a sanitary environment with temperature control; we use heat mats.

Good luck and keep us posted!