I ask people to have their dog walked and fed before they arrive. I prefer just one handler so that the dog is not distracted. When the dog owner arrives and before the dog leaves the car, I bring the owner into the studio to see the set up. I tell them where I would like the dog to sit and how the owner can avoid standing in front of a light.
Once out of the car, the dog gets a chance to smell and mark territory, I don’t even say hello, it is better not to make a great fuss so everything is calm and the dog will stay relaxed.