I think so often the way to successfully help students to understand complicated texts is to be able to present a key idea or theme to them and help them to understand it in their own context and time. This, in my experience, acts as a kind of link or hook that the students are able to use to understand the rest of the text.
In this Faulkner classic, the key idea that needs to be highlighted is the way in which this text deals with the Compson's deterioration as a family, both in terms of their wealth and the accompanying moral deterioriation that occurs as a result. It might be worth asking students to investigate famous characters from their own experience or from the media that have had everything fall apart and the impact that this has on their character. For some reason, the character of Mel Gibson sticks in my mind and the way that his deterioration has resulted in his drunkenness and other various failings. This might help your students to focus on the central aspects of this text and give them a valuable bridge to understanding what happens through relating it to their own experience.