Meditations from the Otherworld

Silly man that I am, I'm not sure I see any real grail in the Spoils of Annwn. Maybe the real test is to see if we can trace the grail themes throughout the Mabinogion. The other branch, with which I am less familiar, that of Branwen, Daughter of Llyr, supposedly contains the "wounding of the king" topos. Is that specifically a "grail" theme? Does this story contain any real relationship with standard grail legend?