Yup...been there, done that with my daughter's stupid Dalmation. It took 4 of us to hold him down and pull the quills out of the roof of his mouth. We used that baby antiseptic called Numzit to deaden the pain and needle-nose pliers to pull the quills out. Bad part is, the stupid dog did it again two weeks later. He also turned out to be a serial chicken/duck killer. We came home one day and he had massacred 6 chickens and 2 ducks, the feathers covered half an acre. Unfortunately, they were the neighbor's chickens and ducks so we had to give him away rather than see him shot if he did it again. Personally, I was glad to see him go.
When I'd have a young dog develop that porcupine thing; I'd just leave them in woods and start with another pup. I think that's how it was always done to get better hunting dogs down thru history.