The waymarking from Montpellier to Castres is a bit patchy, and it does tend to go quite pointlessly around some village centres (taking a roundabout tarmac road instead of the one going into the pueblo that's always been on the Camino, really ??) -- but having said that, it's basically a really easy route with multiple possible variants all headed in the same direction over similar terrain on that particular section, so there's no point worrying about getting lost.
But that's the Arles Way, not the Piémont.
The Piémont is still quite sparsely waymarked.