Hi
For routes and maps, try either the RAC Routeplanner or ViaMichelin (both online - Google will throw them up as the first choice)
I'd be tempted to cut across into Portugal and then down the coast rather than a more direct route/straight line through Spain as that would be much more interesting
There are loads of campsites, especially toward the coast - they often have a collection of flagpoles at the entrance so you can see them from a way off.
In the past I've just followed the general route and started looking in the late afternoon. That way you can vary your day to suit the conditions or how you're feeling, without being tied into getting to a cetain point by a certain time
Have fun
