You really can teach an old dog new tricks.
My own Lettie is pushing 12, has her moments where she's stiff and moves slowly. Her hearing is diminished, and there are days where I think she's just completely deaf. Other days there's a little more hearing than others. I suspect it's all connected to her age and thyroid meds. I also suspect its her just saying "today I need a day off for good behavior".
I've always taken the attitude that she's a highly intelligent dog, being a McNab Dog. Think of a Border Collie that is more mellow and smarter than average, but a McNab is really it's own distinct breed. We sometimes call her Stealth Dog because she hardly ever barks unless something is truly exceptional.
Since she's so intelligent I thought teaching tricks is kind of a waste. We would teach my canine prodigy complex behaviors like "Go Home". Go Home was when we'd get about a mile from the house. She's never gotten lost although she tends to take her own time getting there.
Another thing that I started doing from the beginning was to try to associate hand signals with those commands. Some worked better than others. Yes, Sign Language for a dog works, and if your dog still has hearing it is the best time to do it. Start early and you'll be ahead of the game.
Besides, English is not a dog's first language.
One of the more useful behaviors was the "Show Me". Show Me would give her the option of telling me what SHE wanted and I would follow through. It's not always food or cookie, sometimes it's walk or yard. Since the leash is in a bowl on the dryer in the laundry room and has been since we moved into the place six years ago, if she wants a walk, she will lead me to it.
Show me is now hands held out to the side and palms up.
She's training me to be quieter which is an amazing challenge in itself. It is a bit of a shame because I found I tend to talk to her when I'm out walking. She hasn't responded in kind but she used to listen because she'd look up from time to time and give that smile that dogs do.
It also is making her a bit more frustrated. Since I tend to wander around the house, she may not hear me get up. That's when she shows me she still knows how to herd since she is looking for the stray by performing a perimeter search until found.
We're having a bit of work done on the property and since I saw the truck drive off, I went out to have a quick go at what's been achieved. Happily I walked back into the house to two worried brown eyes coming around the corner at a trot. The one that got away has returned and the herd is intact. From the side of the house I was at, she could not see me through the porthole and was shuffling from room to room sniffing and trying to crane her head to see if she could spot me.
If you're around town and you see some guy gesturing to his dog, say hi, it may just be me.