Essentially it is death energy in powder form. If desired I could see it aiding one in spirit work. However I think the general use is for curses. It is one of the strongest preparations used for such, when created right. Only downfall is you have to use it in person to get the effects.
Goofer dust is not a practice of Vodou, as previously stated; it is a Hoodoo practice. Goofer dust is used against enemies, it is not a protection amulet nor anything of the sort. Goofer dust is usually planted on the enemies porch or in they're footsteps; it is to draw them away or do away with them. It is usually used in the gravest of circumstances, when the enemy actually sets out to do the person harm. There are many effects that goofer dust has but in essence it is illness. Goofer dust can be formed of many different roots and curios, it really depends on the person making it. Common things put into it are Graveyard dirt, snake skin, etc.