i have one customer who i think doesn't vac from one of my visits to the next and she has 2 dogs and about 5 cats, the carpet is thick with hair/fur, i just pre-spray and give it a good brush with the grooming brush, most of the hair is picked up on the brush and what is left on the carpet she is ok with, she doesn't expect miracles.
she also has a chicken that has the run of the kitchen and a duck just outside the patio door in its own paddling pool
colin
ps funny enough when i go there i have always just had a coffee at my last job and don't need one now!