According to the instructions on the tin of the only tooth powder I’ve seen in real life, you dipped your toothbrush into the tin. It was round and shaped like a coffee can. The lid didn’t have holes in it that would be needed to sprinkle the stuff out. Also that powder wouldn’t sprinkle at all, it had hardened into a rock of the stuff. You would have needed a chisel, and mortar and pestle to use it by the time I found it