Check out the free dynamic priest's outfit for M3 at PoserFashion.net. It has several layered pieces: a robe, a tabard, a cloak, a hood. Basically, you start from the inside out, running the sim for each piece separately, and using the piece underneath as the collision object.

There is a limit to how much of this you can do (generally depending on how much memory your computer has). If collisions aren't working properly, it's probably a memory issue. It may help to save the file, close Poser, and get back in again.