I believe there is only one way to hunt porcupine specifically, and that's to do it at night. You might see one during the day, but in a bunch of safaris, I've only seen one in daylight. Spotlighting is the typical approach, and it's not a particularly difficult hunt. You will see (or hear the quills rattling) them on the road or close to the road, and they don't move terribly fast. A .22 works best, since you don't need to blow them to smithereens, but really, anything will do. If you don't want to do a full mount, aim for the head if you can see it, otherwise, centre of mass. Bottom line - if you see one, you should be able to get it. I hit one with a .22 twice, and it wouldn't die. The gun then jammed. The porcupine was scuttling into deep brush, so I got off the truck and, holding the gun by the barrel, used the stock to bash its head in. Hunt over.
I have a full mount and have kept the quills from another for a lampshade. As an aside, when I got the parts list form the taxidermist, it said "porcupine skull (broken)". I should hope so, I hit it hard enough!