If you look at some of my renders, you will see that I have gotten very good with the spline modeler.  I just find it easier to think of skeletons which are easily modified than using the vertex tools which tend to confuse me. :)  I always divide complex items into comfortable to use groups based on what I feel the natural geometries would be.  If you look at my entry for the Halloween contest here, you will see what I mean.  That entire image is modeled with the spline modeler and is over 2000 parts.  Except for the poser figures that is.

I figure that one of the easiest ways to do a clothing item for poser would be to use a poser base figure for a modeling dummy and design the item to fit it perfectly.  Then do whatever other processes you need to do to complete it.