I've had this idea every time I go to the beach and it finally dawned on me I could ask the clay internet. Can you soak a biscuit fired piece in salt water, let it get bone dry, and then fire it and have flashing/salt glaze? ideally a wood fired kiln to max out the texture/flash.
I've had this idea for a few years now, and I can't test it because I'm in a community kiln at the moment. from what I've read once you add soda/salt to a kiln it's going to stay a bit of a soda kiln forever.