User blog comment:Master Moridin/Mercury's Boots Don't Just Shoot Bullets/@comment-226878-20151210160345/@comment-89.142.250.112-20151210161517

It's not like that. Dust is pre-mixed. You buy already mixed combinations. Remember the dust shop? It had loads of dust not just the 4 basic ones. Actually mixing dust during a battle would be almost impossible. The only people who would actually be able to do that would be Dust specialists like the Schnees. Weiss' Myrtenaster is the prime example of combining dust. But it is Weiss' speciality.