Check cord and a pinch collar (not a choke chain). It will take time, but repetition will get it done. Pointers take to whoa pretty well because of the natural pointing ability.
You can be doing anything with the dog (training, walking, whatever). Command a firm Whoa and give a mild tug on the check cord a second later. Obviously, you won’t be doing this while the dog is running.
Once the dog gets a good hang of it, you can start walking to one side or in front of the dog to make sure it doesn’t break. At first, you will want to put the rope around something to keep the rope secured from behind the dog. I just used small trees for this. The dog whoa’s, I walk around the small tree and up the side of the dog (ten feet to the side), like I am approaching a covey. I am able to keep control of the check cord while the dog gets used to me moving in front. Letting you or any other dog take the lead is tough because dogs naturally want to lead the way.
It is no more complicated than that. Once the dog has it down, it is like a magic trick. People come to our house and throw a ball for our dog. My kids say Whoa and the dog freezes. People are amazed. Our release word is “Okay” which the kids use as soon as everyone is done admiring the living statue.