Ever run into a big bull with cows? Can't figure out how to get him away from the cows. Most will say it can't be done. It's very doable. Takes patience and timing.
This is a tough situation. One I absolutely live for. At the end you should be completely wiped out, physically, mentally, emotionally exhausted.
Firstly, you absolutely must have a idea of what the bull is saying and be able to tell when he is getting emotional.
If he won't come in, make him think another bull has come and is stealing a hot cow. For this make him think a cow has been trying to coax him over. Then move back a few hundred yards like 6 or 8 and talk to the hot cow. Then come back up and be the hot cow and move away from the target a hundred yards or so. Then go be the other bull except only go a couple hundred yards away. Then come back. If done properly the bull should think another bull has found a hot cow in his group and is taking her. Pretend you are a cow that wants the other bull. Don't bugle anymore. Become a excited cow and slowly moving away from target toward the other bull.
I've seen it take 3 or 4 hours to coerce the big bull with cows away from his herd.
Be gentle, patient and slow. Its a chess match. Once you unlock the sequence in this scenario your elk hunting life will change forever.
I've seen big bull come a long long ways. To retrieve his hot cow.