Just try and convince a trainer that doesn't do the "positive reward" or "treat based" training methods that their methods are not as effective.
The guy who installed our underground fence has since gotten into dog training. He tried to sell me his services when I ordered a collar for Daisy last year. When I asked if his training methods were click and treat based, he said "behavior modification". When I tried to discuss the benefits of the positive reinfocement methods that helped me with Duke, he scoffed that dogs should learn without bribery! Well - I ended the chat since I knew we disagreed.
And that is when you just "agree" to disagree and know that is one person you will never use…...