Adorable! Spraying doesn't work that well, because it's only a small amount of moisture. Pour some water right into the substrate to moisten (not dampen) it. Then mix it up a bit with your hand so it's nice and moist throughout. It's fine for the top few millimeters to dry out, as long as the subsurface layers stay moist. However, they can dry out after a while, too, so every few days to weeks (as needed), just add some more water and mix again.