Thanks for the info! I'm not sure how to squish the foam "like a sponge" since it's trapped in the plastic cage / wire grill assembly, so I might have to air dry it or put it in a low humidity environment, like you mentioned.
Does anyone know how to open the grille on a Shure SM57? I soaked the whole thing in warm water and dish soap and rinsed it, but I think it would get cleaner and dry faster if I was able to separate the foam from the rest of the pieces.