Hi Alexander,

Data from ~10 subjects require qualitative methods for analysis and interpretation. The research methodology depends on your research aim. A qualitative study is a good start for the development of a survey when you want to identify the right and best questions to capture the concept of interest, in your case "diffusion" for example. But if you want to use quantitative methods, once the survey/questionnaire is developed, or used in a new population, you need to assess its psychometrics, and a convenience sample of about 100 participants to do that. If your test has good psychometrics, it can be applied on large populations. Maybe the paper below helps:

Nelsona, Earleb, Howard-Grenvillea, Haackc, and Youngd, 2014. "Do innovation measures actually measure innovation? Obliteration, symbolic adoption, and other finicky challenges in tracking innovation diffusion". Research Policy, Volume 43, Issue 6, p. 927–940

Best

The Delphi Forecasting Technique (or 'expert consensus methodology') is a useful qualitative research technique for gathering opinion from experts, including reaching consensus about a topic or likely outcome. This paper neatly describes the application of the method in selecting the most important actions to include in policy guidance.

http://bmcpublichealth.biomedcentral.com/articles/10.1186/s12889-016-2822-6

Another suitable approach is the Key Informant Interview.  Although the paper below recommends a minimum of 15, I think of it as information value - the first 10 experts will add far more information to what you have now than experts 11 through 15.

http://pdf.usaid.gov/pdf_docs/pnabs541.pdf