For sushi rice, I rinse several times, stir the rice into boiling water. It's enough water to cover the rice plus a bit more (maybe 30% more by volume). I keep the heat high and stir until it is all boiling and then I turn to whatever the lowest setting is that keeps it barely boiling. After about 25 min, I uncover and taste it. If the center is still too hard, I let it sit a while longer. Eventually, the center gets soft. If your rice comes out too gloppy, I would reduce the amount of water. If the centers are hard, I would let it sit hot longer.