We use our Jack Russell to bring in the flock. He's not perfect but he does help. In the past we have used a German Shepherd and an Irish WolfhoundxAnatolian Karabash. Apart from the GS, those are not typical sheepdogs and we don't use them in quite the same way. The GS responded well to ordinary words such as 'go round', 'bring them back' and so on, but we never tried 'come bye' and so on, or a whistle.
So it's been a case of learning what the dog can do then adapting how we bring in the sheep to that.
With the Jack Russell, as soon as he knows it's time to round up some sheep, he starts to make a yipping noise - it's very annoying but we have noticed that as soon as he sounds off the sheep know they have to be rounded up, they kind of submit and instead of running off in all directions (as primitives can do
) they start to head in the right direction. We usually use him between the two of us, so he runs back and forth between us, not letting any sheep through the invisible line he makes. He can also be used by one though and will run round in the direction we indicate. Sometimes he's an idiot and cuts the flock in half, but then we just start again.
We do use the bucket method to move the flock from field to field, but as soon as our sheep know we want to catch them they tend to b###r off, hence the usefulness of a dog - they seem to respect him, in spite of how small he is, far more than they do us. They know they can run rings round us on our own
For most of the time, ie when we are not rounding up the sheep, the JR wanders around amongst them and is on excellent terms with them. The GS used to ask them politely to move, and the giant wolfie cross just used to stand there creating a blockage, or go up to the group we wanted, especially the Soays, then we would call her back and they would follow her
So what I'm trying to say is that if you are using a dog which is not typically a sheep dog then how you use it would be different. Rather than sending her off to be trained by someone else, it would be better for you both to learn together so you can work together in a way which suits you, your dog and your flock. It doesn't happen overnight either.