Idea effects - Creatures into dust

In my idea, when the circle of light hits the evil creatures they turn to dust. I imagined this would be done using camera and editing techniques. Simply by filming the creatures, then stop the recording removing the creatures from the shot, start recording again and throw a big handful of collected dust onto shot where the creature was stood. Then using simple edit techniques cut the shot together in the right place to make it look like they have simply turned to dust: An example of this was done with coins in 'Edger Wrights' - 'Scott Pilgrim vs the world'. Here is an example of the same effect someone has done and uploaded to youtube.

References:

Scott Pilgrim Coin-Burst Effect (KO) (YouTube Video) [online] last accessed 17th December 2012 on http://www.youtube.com/watch?v=egdFChekChE