a really good dog should follow instructions from anyone as long as you are using the same terms.
A good farm dog may be *required* to work for other handlers, in which case, in *that* context, a good dog would work for other people. But to have a dog win trials with you, it needs to have bonded with you, and that's a different thing altogether.
Some, if not many, of the very best dogs will only work for their one handler. Alan Bradley, who trains and deals in sheepdogs, and who has won the International at least once, told me of a dog he bought that took
a year to bond with him and work for him. He wouldn't have kept it that long unless it was a really good dog - and sure enough it did go on and become an excellent trials dog with him.
He does train the dogs he sells to work for different people (he trains them using all kinds of different voices! so funny

) , and the dog I bought from him will work for other people - he even worked for a loopy actor in a Brazilian film...

My own dog (by which I mean, the one I trained myself) will only work for me, and I like it that way. BH's dog arrived fully trained and he couldn't get her to do anything, because he doesn't use the 'right' words / sounds. I could get her to work for me, because I did use the 'right' words, so we knew she had it in her. So he kept her and worked with her to learn his way of working. Now of course she works only to *his* funny noises, and won't do a thing *I* ask her
