I use Cinema 4D and model around the base morph and scale of V4 at zero pose (except for shoes, see below).  I use interPoser Pro to import the figure and to apply morphs for certain things, and to allow modeling around a posed foot for shoes - the ONLY situation imo where you should not model around a zeroed figure.

For shoes, since the zero pose foot is at a shape that makes no sense for a shoe, you either have to model around that and pray that your shoe will look okay when the foot is posed, or model around a posed foot and adjust the rig to compensate, when you bring it into Poser.  In older versions of Poser this isn't always possible (Stephanie Petite 3 in Poser 7 or older, for example).

For every other kind of conformer, you really want to model around a zeroed un-morphed figure or it ends up being a huge amount of extra work when you get to the rigging stage.  You can try to model around a morphed character and still get it to work sometimes, but the garment will be much less flexible and won't deform the same way as the character when posed.  There is very little leeway when trying to rig a conformer whose base shape is substantially different from the base shape of the character you're trying to rig it for.  This is why you see so few clothing items that perfectly fit drastic morphs like The Girl - it's so much work to get stuff to fit perfectly and pose well.

Sometimes I sketch in 2d but most often I just sketch in 3d, essentially modeling in low poly techniques around a figure and seeing what will work.  Since I am not very good with 2d but I'm very comfortable with 3d, I'm pretty productive with this technique.  Using the modeler's features of point snapping makes this pretty quick and visually effective for me, since you can turn the camera and look at what you're doing from all angles to see if it really works.  If you draw very quickly and/or are very comfortable with 2d visualization it would be a different story.

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