As you know, we have some elderly sheep, but we have never had a deaf one. We have had a couple of old sheep which became blind and they have shown an ability to learn and to adapt which has surprised us. Not knowing what your friend has tried, I shall tell you how our old ladies manage and you can see if anything sounds applicable. First off though, one of our dogs is now quite deaf and we have found that the only ways to get her attention are clapping loudly, and shining a torch between her and us when it's dark. The clapping has to be of a certain pitch, so that might work with the tup, but you would need to be close to train him. Similarly a torch might work at night.
Experience with our sheep has shown that we will never be without the shovers from the rest of the flock, but our old ladies learn just to shove harder, as soon as they can smell the treats (yep - digestives! Also Tup and Lamb which has a sweet smell) So if the tup wants a treat, he'll have to push to get it.
We find that the sheep cannot hear when it's windy, so calling, clapping and so on don't work then, and they go hungry. At any other time they recognise our voices - your friend should try calling both high and low, and make sure the tup is close when she does this at first. Rattling buckets and rustling biscuit wrappers work over a great distance - worth experimenting with in case the tup has one of those within his hearing range. Our sheep have also learnt shouted commands such as 'turn RIGHT Elfie', 'Careful, Elphie', 'This way, Elphie', STOP, Elphie', and so on - you can steer a sheep that way rather effectively once they have learnt the calls - negative reinforcement is usually when they collide with something!
I suggest your friend makes sure the tup's ears are clean inside, and free of hanging fleece, the same with his eyes.
As I've been typing, I have felt increasingly that the torch, even in daylight and strong winds, flashed across his eyes, but never shone directly in them, will attract his attention best.
All this may be no use, but you never know.
Incidentally, when you are driving and there are birds in the road, flashing your headlights at them is far more effective that sounding your horn to shift them away.