3D Paintbrush is a technique that uses text descriptions to automatically add textures to local semantic areas on a mesh. The method operates directly on the mesh to generate texture maps that seamlessly integrate into standard graphics pipelines. It simultaneously produces localized texture maps for the specified editing areas and corresponding textures tailored to them. We utilize multiple stages of a cascading diffusion model to supervise local editing techniques, thus enhancing the detail and resolution of texture areas. This technology is known as Cascading Score Distillation (CSD) and allows the distillation of scores at multiple resolutions in a cascading manner, providing control over the granularity of supervision and the global understanding. We demonstrate the effectiveness of 3D Paintbrush in adding textures to various shapes within different semantic regions. It has functionalities such as: