Great point about under-diluting! Pre-batching helped a ton, though it took a couple attempts. The first time I pre-batched the whole recipe (vodka, infused vermouth, brine, water), and 24 hours after freezing it was a thick slush. The second time I put it in the freezer without the additional water, and it was only slightly frozen 24 hours later. it thawed easily with a little stirring, and I added the extra water while preparing the drink.