This practice is easiest to do in a sequential order, where participants take turns. If you do that, please remind people that it's useful to have a little space between phrases, to receive the aspiration. That said, this practice can also be done spontaneously, by inviting folks to simply say, "May It Arise." This usually works best after doing it sequentially for a while, so that the "It" is clear in awareness. It's also easy to parlay this practice into the Pith Metta practice, if you want to play with a different group size or find another way to introduce a spontaneous order.