It takes training and consistency. I started it when mine very first went to the outdoor pen.
The are capable of learning.
Having them in a pen makes the training easier.
You really do need to get them penned up. Get some friends and herd them like he did initially to get them into a pen...
Do you have a pen to confine them to once they are out?
Have a friend help with this...
Take a long rope, one person on each end and walk slowly on opposite sides of the pond. As the rope gets close they should swim away from it and toward shore. Once out herd them into their pen. I would not...