I would just like to add another alternative for this achievement.
In the "The Last Crusade" level, the final stage is "The Temple of the Grail." At the very end of the stage you will come to a room with about 50 Grails. Once you defeat the knight, he will stay down. Open up the two sections and just start whip grabbing the Grails. It should only take about 5 minutes depending on how much you have played the game.