Many existing applications suffer from inherent scalability limitations that will prevent them from running at exascale. Current tuning practices, which rely on diagnostic experiments, have drawbacks because (i) they detect scalability problems relatively late in the development process when major effort has already been invested into an inadequate solution and (ii) they incur the extra cost of potentially numerous full-scale experiments. Analytical performance models, in contrast, allow application developers to address performance issues already during the design or prototyping phase. Unfortunately, the difficulties of creating such models combined with the lack of appropriate tool support still render performance modeling an esoteric discipline mastered only by a relatively small community of experts. This article summarizes the results of the Catwalk project, which aimed to create tools that automate key activities of the performance modeling process, making this powerful methodology accessible to a wider audience of HPC application developers.