Designing hull surfaces (and other surfaces as well) is usually best done by direct editing of the surface's control points. This approach will almost always yield a surface that is more fair than building a surface by using Rhino's loft, sweep, or network commands.
There are many ways to edit the control points, beginning with simple dragging of the points. Rhino and Orca3D have a number of features to help with this; Orca3D's construction planes for editing in the Perspective view; Rhino's osnaps, snapping to the grid, and ortho; and of course the real-time update of sections and hydrostatics that Orca3D provides.
But there's more to editing control points than simple moves. Rhino has multiple options for scaling one or more points, Orca3D's 'orcamove' dialog makes it easy to position points relative to one another in Cartesian or polar coordinates, and with Rhino's 'rotate' command you can rotate a single control point or entire row or column.
There are other useful but less well-known commands, such as 'moveuvn' which allows you to move control points in the u, v, or normal direction, 'setpt' which makes it easy to align a group of control points to the same X, Y, or Z value, and others.
Brian James of Robert McNeel & Associates has put together a nice introductory video that describes control point editing. Even if you're an experienced Rhino user, you might pick up a tip or two. To watch the video, go to http://vimeo.com/album/57041 (there are a number of other Rhino-based tutorial videos there as well).