Due to the increasing use of general purpose graphical models (e.g., UML diagrams) and domain specific graphical models in different stages of software development, software engineers who work with these models spend more time interacting with modeling tools. Thus, the usability of interaction techniques of modeling tools affects the overall productivity of software development. Tool developers and user interface designers rely on the feedback from usability tests to optimize the user interface of tools that provide a graphical editor. Developing a working prototype to test new techniques is costly due to the complexity and variety of graphical models. This results in either tests at the late stages of development when changes are more expensive, or tests with prototypes that only support a subset of the intended graphical models, thus not comprehensive. In order to simplify conducting usability tests, instead of using the intended graphical models in the tests, we propose to use simpler models that require similar interactions when being manipulated. For this purpose, we introduced ImitGraphs, an extended graph with additional properties so that it can be specialized in interacting similarly to an intended graphical model. Then, we designed a method to instruct test participants to create ImitGraphs. Specialized graphs enable us to develop prototypes for usability tests faster and consequently cheaper resulting in more usability tests at early stages of tool development and on a wider range of intended models.