Depends on the dog. With Terra and Kimber, it was basically a forced hold. I put her in a corner of a small room, stand next to her, put the dumbbell in her mouth and make her hold it. When she put it in her mouth, I would "out" her, release her from the corner and reward it. Once she understood to take the dumbbell, I started smacking the dumbbell to make her hold it tight without chewing on it. Once she would take it and hold without chewing, I would start to have her work on fronts with it and starting to heel with it. To the point of doing a full OB routine with the dumbbell in her mouth. Then I started to hold it out in front of her, make her lean forward and take it, gradually increasing distance and going closer to the ground until I could start tossing it.
With Areli and Xander, it started similar, but then went to a play retrieve. It's what made sense to them. Trying to "force" them created a lot of conflict and issues with the retrieve. Going to a play retrieve, helped them. Personally I go for option 1 as for me it seems more reliable. But again, it wasn't working for Xander and Areli.
Heidi was started with a play retrieve, then added some of the "you have to" to it. With Heidi she would screw around on the retrieve to the point of taking Kiersten out during one of their P2 titles haha.
My older female is ball crazy, toy crazy. She hoards all the toys in the house. So, I was able to transfer her drive for retrieving a ball to the dumb bell. She will actually bark to get me to throw it. The big thing with her that I never figured out how to break her from - was she would pick up the dumb bell by the bell, not the handle. (I retired her from schutzhund before she perfected her retrieve.)
My younger one, I started out prying her mouth open to take the dumb bell, then petting her head while she held it for a bit, then rewarding her with a treat. Gradually, she got so she would take it on her own. Then, I began asking her to follow me (facing front) for a short distance before letting me take it out of her mouth. Then, I get her to walk by my side, do a front, let me take it from her, then fuss beside me.
As she's gotten used to the dumb bell, and retrieving a ball over the jumps, she's gradually getting the idea that she should retrieve the dumb bell as well, though she is still not at all consistent with this, and more often than not, refuses to retrieve it. I have a small, light dumb bell that I keep in the kitchen, and I will throw that for her just before I give her her food. She will retrieve it, get a reward, then go to her crate for her supper.
(She'd probably catch on faster if I remembered to do this more often!) But because I have 2 dogs and a cat that get fed at the same time, that makes it a bit tricky.... :rolleyes2:
You could just say "no" and then have him take the DB again and quickly click and reward the hold. Don't ask for length of time until he understands that he needs to take hold and keep the DB or dowel in her mouth until told to let go. I do eventually add in the "out/aus" command just before I click/reward