Here in Brazil we do not have many alternatives for xerostomia and or hipossalivation. I saw a nurse using an intimate lubricant water based in the lips of patients. So I've tried to search for articles for comprove its efficacy, but had no results.
I 've been a subject for testing of lubricant when I was a student of dental school. A resercher gave me two paste for mouth and I used 1 week per each paste. After that, I had Saxon test. The resercher's name is Shuji Toya in Nippon Dental University. I think his article may help you (However, there is a posibility that he wrote the article in Japase....) or his article's reference can help you.