We recently added one night at AKL to the beginning of our November trip. I went through David's DVC rental. They don't offer a one night option, but I sent them an e-mail asking if I could do it. They said they could in situations where an owner had the correct number of points to fulfill the request. I filled out the application with my requested resort, and they confirmed availability within a few hours.
I don't know about working with an owner directly, because this is our first time renting points.