How do you get rid of porcupines

Very carefully.

One of the few things porcupines can't stand is vinegar, but even that is not all porcupines.  Usually porcupines are loners, they just stay out of the way as much as they can, and if they can find something salty to eat they will be back for more.

I keep hearing people tell me porcupines are strict herbivores, but now and then you will find then gnawing on carrion. 

If you use vinegar to stink away a porcupine, you will have to attract him away to somewhere else next.  Usually a chunk from a salt lick will do it, if there is wandfall fruit around to balance it out.

Porcupines drink a lot more water than you'd think, but they only go in when the traffic at the watering hole is lowest.

Porcupines can't shoot or throw their quills but they can and will ram you by backing up fast.

If your dog gets porcupine quills, use a surgical hemostat, grab the quill, split it at the base to tip with a pen knife, and pull out each half slowly enough not to lose a chunk in Fido.  Pull quick enough not to make him suffer worse than you have to.

The worst place for a quill is in his eye.  If that happens, snip the quill an inch or two past the eye and get the dog to the vet pronto.  The less time it takes the better chance you will have to save the eye.

The nasty part about porcupine quills is they harbor tetanus.  It is a nasty way to go.  Get the dog to the vet the next day or sooner for a tetanus shot.  They may want to see what other germs are on the quills too.  Some of them carry rocky mountain spotted fever if the porcupine has ticks.