Warning: this video is really boring to watch. You might want to download it and speed up the playback rate a gazillion times. It's 40 minutes me painting the topology in ZBrush using Polypaint.
This time I didn't start with a plan and included 'subdivisions' myself, making it harder to create a clean mesh (less poles). Unfortunately it didn't make it all the way to complete the rat but I think you'll get the picture. Still, I thought it was worth sharing this and hope you'll find this technique useful for your own project
If you really plan to watch this real time, better grab a coke and popcorn. Enjoy ^^