We used Mr. Winters and now use his daughter. They're the best in the business IMO. Our black Lab went for her first training a couple years ago. We took her after 6 months for her tune up and you couldn't get her within 50' of any of the snakes from downwind. Winters said "I think she got it the first time"
We encounter enough rattlesnakes per year down on the ranch so that she stays constantly tuned up for them.
We met them last time in Bee Caves and there were probably 100 folks there with their dogs. 99% of them were only interested in rattlesnake training. So they had a loooong line. Those of us there for 3 snakes (rattler, cottonmouth and copperhead) went right through without any waiting. I don't understand why, when available, an owner wouldn't want to expose their dog to all three species.