That's exactly what I do, but then with a series of simple shapes. The hard part remains to get a 'bubbling and boiling' cloud in one part, without loose strands. I also tried a setup with a perlin 3D and even voronoi cells and bias, and smooth step functions, inverse blenders, etc, but I'm getting fed up with trying. Up to something else. When the need arises, I'll dig the files up again.