think about it
you're gonna wait for little mushrooms to start growing, then dunk the cake in water for 24hr, then coat it with vermiculite, then the mushrooms are supposed to grow?
if your cakes are in the dark, they might not pin
if your cakes pin, they might not like getting drowned in water
i don't know, i've only done cakes a few times and only dunked/rolled once after the cake had flushed.
i found it best to fruit cakes as soon as possible, as soon as the whole outside of the cake was colonized.