a month ago I developed a gizmo to allow me creating mattes from ID passes quickly and easily when there is no Cryptomatte in the studio’s pipeline. It’s a dynamic gizmo that allows adding as many ID passes as you need and selecting which channels will be part of the alpha. You can download the code from my Github site.
I have also recorded a video showing how this gizmo works. As always, feedback will be welcome and appreciated 🙂