Dog training is an "unregulated" profession, meaning anyone, literally anyone can teach their dog to sit and then charge people and claim they are a dog trainer.
As dog trainers are giving owners advice on their dog's behaviour in order to change it, something that prays on my mind is, what if the owner tries said advice and their dog gets attacked, attacks another animal/human, runs away or their behaviour gets worse as they react badly to what is being taught. Who is in the wrong, the owner who tried the advice given to them or the 'trainer' who gave it?
Accidents when practicing training advice given to you will happen, as that is part of learning, but the risks of what could happen if it goes wrong are potentially huge if the advice hasn't been explained clearly enough for the owner to understand how to do it and the benefits of doing it a particular way to maximise safety for all in the current location you are in.
Does the trainer you are using or thinking of using have any qualifications from reputable organisations that offer courses, do they have any additional knowledge learned such as webinars etc? Always check to see what the trainer has and any good trainer will gladly show you what they have and not just baffle you with talk to distract you if they don't have any.
Also, look closely at what trainers tell you to do to stop certain behaviours, does it sound kind, does it get you an instant result, do they tell you "This is guaranteed to work", "It's a game changer" or "Trust me this will change your dog's behaviour immediately", chances are it's aversive in some way and will only suppress or punish the dog into behaving. This has the potential to weaken the bond and trust between you both or confuse the dog as it might not understand why its owner did what they did.
Experience does matter, but is that experience right for you and does it match your ethos when teaching a dog how to behave. Are they self taught? Is that experience actually beneficial to dogs not just behaviourally but mentally too, does the dog engage happily during the training or are they just reacting negatively to the type of training?
I've said it before, if a dog has to be punished to stop a behaviour, then it hasn't been taught how to the correct behaviour.
Dog's who have behavioural issues, have found that doing that particular behaviour is massively reinforcing (rewarding) to them, the person they barked at went away, the stress/nervous bite achieved the same result, pulling on the lead gets their owner so frustrated they give in and allow them to pull them more and criss-cross in front of them all the time...
Teaching a new behaviour will take time as the dog needs to know 3 things:
1) Your dog needs to know the training is fun,
2) Your dog needs to know the training is rewarding (reinforcing to them)
3) Your dog needs to know the training is safe.
If your dog doesn't believe any of the above 3 things, or 1 time you revert back to the old ways because "It's only once and I'm in a rush" then it will be much harder to progress as your dog will already know the old way is 1,2 and 3 as it's been doing it for so long.
Remember these 3 important words when training your dog: Repetition, Persistence and Patience and by making sure the training is fun, rewarding and safe, your dog will learn to adjust to the new behaviour meaning the old behaviour will slowly fade way as long as you don't give in once and continue with the new behaviour as though it's second nature to you.
Training your dog is just as rewarding for you as it is for your dog, so make sure you enjoy it as much as your dog does!