here's a screenshot of what i'm doing now.
it might look a bit diseased, but there is a good reason for the way it looks, it's actually two models. there is the original subsurf model, which is red and then there is the triangle based model which is pink.
i'm using the subsurf model as a guide for the triangle model. as i move the vertices of the triangle model around i can see the red patches appear or dissapear, which lets me know how close it is to the original. as well as helping me keep the shape of the head correct it also means that everything is ready if i need to generate a normal map.
here's the blend file if you want to take a look.