I train protection dogs and Im sure I will get butchered for this. Anytime you use pain to get a dog to do something, you will create a flat and unreliable working dog. The degree of unreliability will depend upon the trainer as well as method. Think about it, would you rather go work for someone who praises you and gives you bonuses every time you do something right. Or would you rather work for someone that pinches you all day till you do something right. There is a difference between correcting a dog for what he does or does not know. For example how can you correct a puppy for not sitting the first time you ever give him the command. He has no idea what you want from him. That said, when you have a pup or dog who knows sit every time you give him the command, and then when he decides to disobey you when you give him the command, now it is time for a correction. To answer your question, obviously your pup likes to chase after a dummy. Take two dummys, throw him the first dummy. When he bring the first dummy back, hold the second one up but dont throw it, just let him see that you have one and are ready to throw it. This might go quick or you may have to wait for a while. Give him the command you will use to have him drop it. As soon as he drops it, throw the second one for him. This has to be instant so that he gets it. He will learn, the quicker I get the dummy, bring it back and drop it, the faster I get to fetch another one.