Operations to reconstruct your beauty pass are just plus (Linear Add in Adobe softwares) or multiply. There’s more detailed information in Blender manual. Some render engines have different setups, but there’s always mencioned in their respectives documentations.
Passes: https://docs.blender.org/manual/en/dev/render/layers/passes.html
You can check this EXR-IO Plugin Photoshop tutorial about combining render passes, same applies to After Effects:
