It is not necessary to bevel the edges (depending on what you want your crease to look like).
I did use the split poly tool in some creases. For example in the line around the door there are actually three lines in a V shape with a full crease on the bottom and a double partial crease on the top edges. But on the footstep under the door I only used a double partial crease.
The more partial creases you apply the more the sub-d will look like your proxy. Sometimes if you bevel you might not need to crease the edge.
Take a glance at my <a href="http://forums.simplymaya.com/showthread.php?s=&threadid=9428"><b>Porsche 959</b></a> WIP