IMO It is not as simple as showing a dog a dead snake and shocking it. I think handling any snake in front of a dog is a bad idea. An owner should show signs of fear from any snake to help the dogs realize the snake is bad and avoid one at all costs. Dogs will investigate anything the owner is doing.
There are several stages to the process.
My friend Web Parton, bird hunting author, retired bird hunting guide, and dog trainer offers snake avoidance training.
https://www.snakesafe.com/ One important aspect to this avoidance training is the trainer's ability to read each dog. The trainer is the one deciding when to administer the shock. There are varied reactions and Web is good at observing this.
First is the introduction to a snake. He has had a seasoned dog there in the lineup. One time he asked me to bring my female GWP who had been trained before. When he produces a rattler and puts it on his carpet my dog heard the buzzing and immediately begin to growl. The newbie dogs become very alert knowing something is wrong.
The trainer will bring each dog to the snake. Most dogs are curious and with careful placement of a fairly docile rattler, like a blacktail, the trainer can have the snake stay put. (all snakes used are defanged just before the session) When the dog gets too close it will get a shock.
Next step is scent recognition. The owner brings the dog on a lead downwind from the snake. When the dog shows a sign he smells the snake he gets a shock. All dogs in the training session will do the downwind exercise. As each dog is frightened this will end up with other dogs knowing something is wrong before their turn.
Second is the sound session. Same concept except the dog is brought in upwind. When it investigates the sound or shows signs it hears the sound, it gets shocked.
Third exposure, the sight session, is done in a similar manner to all dogs. Snake is placed out in open. Owners take dogs on walk then bring the dog to where it can see the snake. When it realizes the snake is there dog gets shocked.
Then a snake is hidden in an area nearby. Owners will take dog for a walk and go into wind towards snake. When dogs shows he smells the snake he gets shocked. This process can be repeated a few times in various settings till the particular dog responds properly.
All my dogs have been trained this way. We get snakes including rattlers on our property. The dogs will not approach but give a warning howl that is unique and I KNOW there is a snake. Sometimes it is a bull or king snake. I always remove the dogs immediately and either move the snake or in the case of a rattler it gets dispatched.
Regardless of how well a dog will respond to a rattler there is still the chance of a dog getting bitten. A dog can be moving quickly through the brush and encounter one before there is a scent or noise to alert the dog. My youngest dog got hit a year ago May. The dog knows about snakes and it is good at avoiding them but this time I figure he ran by it. Hind foot got nailed.
I recommend you get the vaccine for your dogs too. While the dog may still require some antivenom it will help lessen the effects.