Thats for really conforming clothing.
There's another option you could do for a looser item like a heavy coat. Do the copy/paste method above, but do it only for a ring around the torso. Clean that up to reduce the number of poly's, then just extrude it up one row at a time, and adjust each row as you go.
It would be a lot like creating a new torso from scratch, but it may end up being easier on you than trying to simplify a high rez poser model down to the point you can use the above method.
But, thats the beautiful thing about this hobby/profession/whatever, there's always a million different ways to do the exact same thing, you just find the one that works best for you in any given situation.