Blasting or 'blastin' in folk Magic, generaly means to interfere with or destroy things. According to lore, witches blast as acts of revenge or unprovoked malice. Blasting powder or at least our blasting powder isn't so much a magicaly charged or programmed hex or cursing powder, but is instead really raw power itself. As such you could technically use it for any form of intense magic which involves using a forceful and strong approach. Think of it as a magical bomb, it's neither positive or negative it's just raw force.
When using this powder please remember that it is fast acting and is designed to highten the impact of anything it's used in. If your wanting to take a subtle approach to your magical working then you probably wouldn't use this. If however you wanted to do some fast acting money magic, or some kind of offensive or defensive magic, then this might be a great ingredient to add to your spell.
It works best as a base for your spell but that doesn't mean you couldn't energise it and programme it to be used on it's own.