I haven't done the Primitivo but a few returning pilgrims have said that it was really difficult terrain. Received an email from a fellow last week (who has done the Norte, Frances, and the via de la Plata ) and he said: "The primitivo is the toughest thing I have ever done. Even as a 19 year old in the army, this was tougher. Afrikaans word af*** just about describes it. But, wow!!!! It was something else."
I think you might want to consider boots!