The Stick model is a Multi-degree of Freedom system consisting of a series of story-level lumped masses connected in series by non-linear shear springs suitably calibrated to simulate the interstory behavior. The Stick model has been recently introduced to predict the seismic performances of existing buildings in terms of engineering demand parameters, such as interstory drift ratios and peak floor accelerations, both at the building and at the large-scale level. This model has been demonstrated to predict the damage concentration and distribution with sufficient accuracy still preserving computational time with respect to refined finite element models. Previous works proposed a calibrated model to represent the behavior of existing gravity load-designed infilled building typologies. Recent advancements suggest the adoption of simplified procedures to generate interstory shear spring backbones allowing the extension of the model to different building typologies also accounting for possible retrofit interventions. In this paper, a simplified procedure is proposed to generate interstory shear spring backbones. The procedure allows generating interstory backbones accounting for typical features characterizing existing buildings, explicitly simulating typical failure modes of non-conforming RC elements, infill-induced brittle failures, and introducing the effect of possible retrofit interventions to increase both the building structural capacity and the stiffness.