Masking objects behind glass?

[Streetwise]

This is probably an age-old question, but what is the best approach for post-work to objects behind glass, specifically when pulling masks? I'm thinking of two passes - one with the glass hidden, and the other one, I'm not so sure about... If there was a way to render just the glass with an alpha? I could then add it back in as a Multiply layer in Photoshop, but how would I set that up? Maybe it wouldn't matter? Thanks in advance!

[fixeighted]

Multimattes work when the glass is set to affect all channels

[Streetwise]

Multimattes work when the glass is set to affect all channels

That makes sense. I will give it a whirl!