Oneounceload and olddrum1 are correct. To a comp shooter, dust is what comes off a "close, but not close enough" lost target. That being said, we know the OP means what's known as a smoked, powdered, puff balled, ink blotted, black cloud, vaporized, or any other description of a target hit, as 1-oz said, "so squarely there is no visible piece."
How to smoke a target? Practice, Practice, Practice. Of course, a load that concentrates a much shot as possible on the target helps. The closer the target, the more likely it's going to get vaporized. (In my younger, crazier years, when we were closing down the club for the evening, we'd play chicken skeet. We'd position ourselves at the low house target stake and try to hit the approaching target as close to the end of our guns as possible. This would result in some spectacular breaks.)
It doesn't take a heavy load, .410s puff ball targets all the time. Also, it doesn't take a hot load: often lower velocity loads are more center dense than their faster cousins and smoke more targets. Vaporizing targets may look great; but, as was previously mentioned, it usually means you've traded off a larger kill zone for harder hits. There's an old saying in the comp shooting circles: "I'd rather dirty chip 100-straight targets than ink ball 99 and miss one." There's no style points on your average card. That being said, one of the most satisfying aspects of shooting is inking a skeet pair from station 4 with a .410. You know you're having a good day.
Also, if you're impressed by the factory demonstration shooters ability to smoke 'em up in the videos, don't assume they are shooting the same targets that you are. As RoscoeC indicated, not all targets break the same. Shooters want targets that are easy to break. But, gun clubs want targets that don't break before their time. Targets damaged during handling or while in the trap machines don't make any money. And, the target manufacturers have a lot a wiggle room with their product. Here's the complete NSSA 2009 target specification:
[SIZE=-2]SECTION I - EQUIPMENT
A. TARGETS
Standard targets of good quality measuring no more than
four and five-sixteenth (4-5/16) inches in diameter nor more
than one and one-eighth (1-1/8) inches in height shall be used.
B. AMMUNITION...[/SIZE]
Just what is a "Standard" target is up for interpretation.