Around 10 yes, most of the work happens in the shader. The GML side is more about sending shader uniforms.
Viewing post in Sketch (Cartoon) Shader [Post-Processing] comments
No, not on Discord. I usually include tutorials on my website, but to be honest, there's no secret to how this effect works; it's basically a shader_set (the shader does 90% of the effect), surface drawing, and uniforms. At this point, you'd probably be adapting it to your specific project, and that's usually what the user handles.