Have been trying to trap a couple porcupines in a crawlspace that inters a work area. Been using a heavily soak cloth with salt and along with salted apple slices. Did this for three days.
On the forth day I added some fresh hemlock bough. Got two the next morning.

Got another porky this morning.

They are fairly easy to catch by trail setting with cage type traps. They seem to take the same route in and out of a den area. Just guide/block them a bit suggesting a route of travel towards and thru the cage and it is usually that simple.