Now in Maya You want to go to your models 'Shape' tab and under 'Mesh Component display' turn back face culling to full. This makes sure you are only snapping your polygons to the side facing you. No we need to make sure everything that we do is going to snap to this high resolution mesh. So go to your tool bar and with nothing selected press the magnet (on its own not the others) icon, this will make your model 'live'. (image 8)
Now look for the icon that's not far from this, with a magnet and a curved line. This is the 'snap to curve' toggle. Once you've done this your all ready to go. (This means that our polygons we're going to draw are constrained to the surface of our high resolution mesh.) If you're using a different app do a search in your help files for how your particular application handles snapping to a models surface. Once you have this done you'll be able to follow this tutorial with no problem.
Set up a material for your high res mesh with your loop texture applied to it. In some apps you'll have to flip your Zbrush colour map vertically. Once this is applied to your model make sure you can view it in your view port. (In Maya this is done by hitting the '5' key, then the '6' key.) Once you've got your edge loop texture map visible we're ready for the fun part. (image 9)
This is where the fun part comes in, we take our 'create polygon' tool and simply draw each line of polygons as an Ngon (see image). Remember that if you draw you polygon anti-clockwise the normal will be facing you, if you draw it clockwise it will be facing away. We can then go to our polygon menu and 'triangulate' then 'quadrangulate' it and abracadabra one polygon loop! (image 10)
My tip is to work on this in sections, never try and do the whole mesh at once for one very, very good reason.... Crashes. If you PC crashes while part way through redoing the topology your back to square one, so do it in sections and make sure you save regularly as usual. It also helps to outline the areas that you really want to get 'spot on' first such as the eyes, mouth etc. Its worth remembering that you can save some time by doing alternate strips of polys and using a 'bridge edge tool' in Maya or whatever application your using. The reason we wont lose any detail doing this is because the 'in between polygons' share the vertexes of the polygons at either side of it. This can also come in really handy for stitching the various parts together that you're re-topologised. (image 11)