When surfacing models of a symmetrical nature (people, animals, cars, etc.) surface only one side of the head as an example. Change the view so you are seeing the model from the surfaced side in orthogonal mode. Create a screen capture. Load the bmp. file screen capture onto a plane positioned to the models' surfaced side and slide the plane through to the models' other (unsurfaced) side. Then use the screen capture as a tracing guide for building the other sides' boundary curves.