Mom, in Hospice, is fading fast today. What is the best way to comfort Dad while we each deal with our own grief?

i suspect that everyone deals with loss in their own unique way. id suggest just paying close attention to what your dad is saying. some small comfort might be overlooked if your not listening closely enough to him.
im close to losing an 89 yr old aunt and its going to kick me squarely in the ass when it happens, inevitable or not.

Just be there, hold hands. Recall a happy moment, and try to make her end of journey as pleasant as possible.
God bless,
L