A prong collar is how you physically control a large dog if you're a smaller person.  A proper prong collar, like a proper e-collar, is another great tool.  It's simply not possible for them to fight against the prong collar, and a well made one poses no risk to the dog.  You also have to learn to use it; most people pull back parallel to the dog, but it needs to be pulled up.  Also it needs to be high on the neck, not on the shoulders.  Another tool our trainer left us with.  We use Herm-Sprenger collars on her recommendation.  We tried a cheap one from Petsmart--total junk.

We have used a prong collar and yes it does control the dogs on a lead. But it does not allow you to let the dogs off lead. You cannot use it to train them to sit, stay and come. So it is very limited.

I would like to thank those who posted all those very helpful ecollar suggestions. I would not have thought of the 'sit' solution to our dogs wanting to take on other dogs. So if you have any more I'm ready to listen and implement them. The collar is supposed to be here today and unfortunately I ordered one before I saw the suggested vendor. We'll work with what we have and maybe hand that down to my daughter who also has a dog and order that one.

We use them for training, and we do let the dogs off leash and leave them on.  Then use the e-collar for recall, then put them back on the leash.  Both are great training tools.  Again, all done under the supervision of an accomplished trainer.  She showed us how a sharp but not hard snap upward on the prong collar teaches sit.  And a pull to the ground trains a down.  There are half a dozen things she used those collars to teach.  Again, it must be a high quality version with zero binding.  It must squeeze and release instantly.  It's the light and not painful pressure that will train a dog without negative effects.

Also now the collar going on says "we will be in working mode" and they pay more attention.  The prong goes on for all training even if we won't use it, and only use the e-collar.

I was very interested in these for a while. But after reading a few stories of e-collars malfunctioning decided clicker and treat training was the way forward for us.