I wanted to write my experience walking the Camino del Norte in the reverse direction for people who wish to do the same in the future:
How well it is marked in the reverse direction, varies greatly along the camino, from OK close to Santiago de Comp. to practically nonexistent after Gijón.
The marking stones close to Santiago de Compostela has often a yellow or blue arrow pointing the right direction, but they gradually disappear. In the beginning I really had a hard time finding my way, but learning to ask the locals, seeing other pilgrims and their footprints and using logic, it became easier and easier.
My advise is to get a good guide book which has names of the towns, and even maps if you can get it. In the beginning it may be quite frustrating, but after a while it'll become a habit, and in the end it will probably not slow you down nor cause too much frustration.
J