User blog comment:Kogath/Monster Hunter 4 Ultimate for the Nintendo 3DS/@comment-4563270-20150116232406/@comment-11537809-20150116232905

You do it by pressing X+A after an attack. It has the phial effect on it (if you have charged the phials that is) and doesn't use up the actual phials/bottles. It also comboes into the Super Burst attack by pressing X+A again