Albertagirl,
That has to be a very interesting and daunting train itinerary. I walked le Puy in 2019 and took a train from Cahors to Toulouse for several rest days and scope out the Canal Midi. (Yucko, frankly it looks like an open sewer as it crosses through Toulouse, I'm sure it is more pleasant out in the countryside.)
I chose to take a Flixbus from Toulouse to Bilbao which turned out to be a magical mystery tour. The bus originated in Rome and was traveling to Lisbon, the departure time from Toulouse was supposed to be around 6pm, the bus finally showed up well past midnight which was hours after the bus terminal was close. One of the stops on the route to Bilbao was in Pau. I have been to Pau numerous times but as far as the two clowns driving the bus it must have been their first. They drove around for about 30 minutes trying to find the station and I knew they were well off course. I think becuase they were running so late they finally decided to forgot finding it, so if there were any passengers waiting to be picked up there; forget it! We fianlly arrived in Bilbao many hours behind schedule but I was only planning on going as far as Burgos, so catching a late afternoon bus was not an issue.