This paper presents a method that allows capture and organization of mental models of all levels of Stakeholders in order to elaborate a System Dynamics Model closer to the reality and more effective on Strategy proposition. This is done through information raised on the application of Group Model Building (GMB), and using PSM specific tools, like Mental Maps and Cognitive Maps. All these tools allow merge opinions and elicitate knowledge from many stakeholders involved on the process. In order to demonstrate the method?s suitability, it was applied on a Case Study to develop a System Dynamics Model for the Flight Test Specialized Human Resources Career Flow. The method has five stages: first, recognize the Messy Situation; second, identify process Stakeholders; third, conduct Workshops and interviews applying Cognitive Maps and, then, GMB; forth, build collective maps presenting a collective point of view for all parts; fifth, build a System Dynamics Model effective and recognizable for all involved Stakeholders, ready to be used as a tool to Strategy proposition to solve the Messy Situation. Flight Test Specialized Human Resources Case Study results show both the model?s effectiveness and stakeholder commitment, based on the proposed method, proving its adequacy.