If you were inclined to walk the
Camino Frances, but want to avoid the crowds, you essentially have three choices IMHO:
1. Walk off-season, start no later than mid-April (Easter is 1 April in 2018) and be off the Camino by early June, when the schools start to get out... Alternatively, start in mid-September, and walk through the end of October.
2. Walk whenever you desire, but adhere to the "pig in the python defense (PIP)." Stay away from all cities and large towns where pilgrims commonly arrive on Friday afternoon by train or bus, and start on Saturday and Sunday. This includes: Pamplona, Logrono, Burgos, Leon, Astorga, Ponferrada, Sarria, etc. Also, this means not arriving on Friday or Saturday, so you can find lodging. You alter your daily distances to keep the PIP in front of, or behind you at all times, to the extent possible. You must be flexible regarding rest days, daily distances and types of accommodation to create time and space for the python to work it's way...away from you.
3. Consider starting at the Somport Pass, walk the Camino Aragones until it flows into the Frances at Puente la Reina; then follow the Frances until Ponferrada. From there walk the final 258 Km to Santiago on the Invierno. This completely bypasses the
Camino Frances from Ponferrada to Santiago, including the much complained about Sarria to Santiago segment. This route is 39 Km farther from Ponferrada, or about two days walking. But, consider what you avoid...
I hope this helps.