Spring will be less crowded than summer, and you can avoid crowds by 1) Leaving earlier (or, theoretically later) in the day than they do, and 2) Stay at "off" cities. Everyone follows the Brierley guidebook, if you get a half a day ahead or behind that, you end up in much less crowded towns, and the walk between them with much less people.
If you leave at the time of day everyone else does, from the towns everyone is staying in, it will be crowded.
If you don't do those two things, you'll hardly see anyone, in our experience (September 2015).
