Usage: All gone is best introduced based on real-life props rather than the flash card. Start teaching all gone by placing a few items, such as balls, in front of baby then removing them and signing all gone. Then start generalizing the meaning of the word by using it with different objects and different contexts, and finally introducing the flash card.
To learn how and when to teach the sign, take a look at the all gone page for a video, diagram, and tutorial.