@Thimios ,
I think @Keith and @mspanic both have had laid out some excellent suggestions above.
One other suggestion I would make is in the best book on forecasting I’ve ever read, Rob Hyndman’s and George Athanasopoulos’ “Forecasting: Principles and Practice” they have an entire chapter dedicated to “Judgmental forecasts”, often used when there is a complete lack of historical data.
At the end of their chapter in section 6.8 they provide a detailed bibliography of other resources and key papers published over the last 20 years addressing the main judgmental forecasting approaches: Delphi, Adjustments, Analogy, Customer Intentions and Scenarios.
Amazingly, the authors have made this entire book available online for free. Here’s the link:
I think you’ll find this material extremely helpful in addressing your question.
All the best.
– Brian