After the one- or two-second sit was well in hand, we extended the time and continued adding more until it was no longer an issue – until Liffey could consistently stay until I released her, however long that may take. As more time is added to her stays, my dog is delivering more value.
When she showed that she was ready, I introduced the further challenge of an actual visitor.
Now, I'm sure that my dog would tell us, if she could, that one of the toughest challenges she had to face in her young life was to keep her rear end on the floor in the presence of her favorite person in the world: her dog walker. But she did do it. Again, at first it was for a mere few seconds; over time she was able to hold her stay until released.*
*Of course, I should also say that this required the cooperation of our amazingly patient dog walker (we miss you, Tami!): she would essentially ignore my dog until released and free to say hello – and then she would physically lower herself to greet my pup, so that keeping "four on the floor" was much more feasible.