Graph models form the basis for flow simulations. In practice, most GIS data are not directly suitable for flow simulations and various steps are necessary to transform grid data into simulation-ready graph models. QGIS provides the ability to create custom toolchains to streamline and automate this transformation process. We (SmartSim GmbH) use QGIS to create simulation models of gas grids for the use of gas quality tracking. The presentation outlines the workflow and the tool library we have developed and how we automate this transformation process with the help of the QGIS Model Designer.