Unsure on that. This my interest check so I can brainstorm.

I figured that it would be like:
* GM posts describing the setting, some items in the area and the actions and dialog of NPC's and stuff of that nature.
* The others post what they're going to do, talking to one another IC and all that.
* Once all the players or most of them post I'll put up another reply describing new areas, reactions and so on. 

But, within reason players can moderate themselves in typical RP-fashion. Like, if the players are sitting in a room just talking about their next plan I don't have to keep posting "The room smells funny. The lights get dimmer" they just keep posting until they do something that requires my involvement. Like entering a brand new area, or engaging in some sort of combat.