Most important will be working a large flock. The dog needs to understand moving a large flock and how to go back on a large flock. A large flock is going to be "heavy" compared to a small flock. When they don't want to move, they don't. I had that today since the fields are full of standing water and run off streams. The dog had to grip and put a lot of pressure on the flock. A big difference.
You don't say where you are located, looking for HGH. Rushville NY is established. I hear there is an HGH in Texas starting up and there is also an HGH in NJ/PA border starting up.