With ZRetopo you can extrude edges and move points along the surface of another object. It's now faster and easier to retopo an entire character using ZRetopo in conjuction with MultiTopo, an IMM brush with 14 different meshes using different topology flow. The great thing about MultiTopo is that it instantly projects the new mesh along the surface of the object. Just choose whatever mesh fits your needs, drag and drop it on the object and it's done.