With a throwing weapon (Flame bottle, knife or dynamite) in hand, enter Dead Eye mode and try to imagine the normal targeting reticule on your screen. The target will not appear, but it works the same. If you rapidly tap R1 then it will be easier. When you release the object (automatic after locking on), the projectile will home in on the target. Try this with a stick of dynamite on birds; the effect is hillarious.