How to skip Decepti0n initiation animation?

When Zer0 the Assassin activates Decepti0n (his Action Skill), he points with his left hand, as if throwing/directing his decoy. One may not shoot or perform a mêlée attack during this animation. However, activating Decepti0n while aiming down sights skips the hand initation animation completely while still activating Decepti0n. What are all of ways by which one may skip the hand initiation animation? And how does one skip the animation most efficiently?