I used GreatStuff Foam again for the brew to look as if it's bubbling over.
I painted the foam with full coat of black acrylic paint.
I applied a fairly heavy coat of mossy green acrylic paint using the dry-bush technique, making sure to leave some of the black undercoat visible in the crevices.
I dry-brushed the final coat using a cream-colored acrylic paint, making sure to leave both the black and green showing through.