How do cerium impregnated disks work?
3M's cerium impregnated material uses their Trizact structure to encapsulate cerium oxide into tiny pyramid shapes.
When water and pressure are applied to the surface, the cerium oxide is slowly released from the structure onto your piece. The pyramid shape provides the friction for the cerium and since it is a direct contact with glass and the cerium with the friction, the polish is highly efficient with minimal mess since there are no slurries used.
You need to be sure to use an adequate amount of water on the pad to activate the cerium. If the water is turning white, then the cerium is being released and will polish the glass.