The purpose of Art-based extension is to help user quickly create painter brush using textures, models and materials you provide, with a single click to install button. The best way to create an Art-based extension is to use the Extension Exporter. In the Extension window, click on Export:
Fill in the information about your package, drag and drop your textures, models and corresponding materials into appropriate slots. Finally, select a directory for exporting the package, then press Export, you would see a script file generated in the selected directory, just give it a second to be compiled.
For best result, your textures, models and materials should be in the same root folder, sub folders for each type of assets are allowed, otherwise your user will not be able to install the extension due to files missing!
After the process, you will see the extension listed in the editor with an Install button. Press the button to test it before publishing the package on the store!