I have the exact same grinder, different design. I went and bought a standard razor blade that just happens to perfectly fit and allows me to turn it along the inside in a circular motion.
I clean the grooves and cracks with the razor as well. Once I have spent far too much time trying to get every morsel, I clean it with hot water and let it dry. You will always waste some...but you waste some smoke everytime you load a bowl and hit it, as it burns in between passing.
Or, if you are smoking by yourself, even a bigger waste!
I like freshly chopped bong snappers, little personal hits that are just the right size to "snap" through but not enough to make you choke and become overwhelmed