Pressure ulcer audits

I am new to the skin care team at my hospital. I am in charge of performing chart audits every week, looking for pressure ulcers and related orders and documentation. My hospital uses a very simple audit tool, in which the nurse places patient stickers on a paper, and tells me if they have a pressure ulcer or not. If they have an ulcer, then they write location and stage. (Easy, right?) I am finding nurses to be very reluctant to assist me with this. I am also finding that documentation is missing, and photographs are not being taken as they should be. Any suggestions on how to motivate my staff? Any suggestions on staff education re: pressure ulcer documentation?