My advice would be to just do whatever feels right for you. I have the Archangel Michael cards myself(as well as most of Doreen's oracle cards) and the whole thing of letting light fill the cards and say a prayer and all that just doesn't gel with me.
I have gone through this procedure with a few of my DV decks, but with most of my decks I simply hold them in my hands and shuffle them just to get a feel of the cards(to infuse them with my energies, so to speak). The response I'm getting from the readings is just as valid and accurate regardless of which method I use to "cleanse" the cards.
Again, just do what feels right for you. Some people don't clear or cleanse their cards at all(especially not if they come shrink-wrapped right out of the factory), some people like to just sit and hold the decks while meditating on it. There are no fixed solutions or rituals that are more or less correct than others. Find your own way and no matter how you do it, the cards will respond to you and your personal energy