I know this is an old post but what the hell...
Millet - Have to use unhulled millet. German or Red. Soak 8-14, rinse2 -3 times a day thereafter in a sprouter, about 3 days total time to fully modified. I've heard you can sprout this in a refrigerator.
Buckwheat - Can use groats or whole grain. same as above only you can soak it for less time and it sprouts faster. about 2.5 days to fully modified.
Sorghum/milo - Whole grain. Same as above.
I have sprouted rice, not sure if there is any value to this for the sake of brewing, but rice likes higher temps, so it take a lot longer at room temp, 4-5 days.
I created sprouters from ziplock reusable tupperware tubs, drilled holes in the side up high for air and poked small holes in the bottom for rinsing/drainage.
I dried in a dehydrator at around 100F for 8-12 hours.
Any idea of the diastatic power of each?
I have heard that Millet is good, Sorghum is best, Buckwheat is fair. Don't know about amaranth, teff or rice.