I've used it. It takes a fair amount of trial and error.
1. Hydroshrink gets sets up fast! I've had it set while I was in the middle of pouring it. A way to counteract this is to put your cups, molds, and tools in the freezer. Use ice water. I even stand in front of the fridge with the freezer door open and pour it in the freezer! It helps give you some more time to knock out some bubbles before it sets.
2. The Hydroshrink is not unlike a hard boiled egg and it tears pretty easily. I use silicone molds and I try to make them so it's easy to get the cast out.
3. You have to mix it fast, but thoroughly, otherwise it will twist and distort as it dehydrates.
4. It works to do a few casts and vary the amount of water. Hopefully one of them ends up the size you want.
5. When the cast is completely shrunken, it will be a transparent amber color. If there's still white in the middle, your results will be misshapen. However, if it's about the size I want and hasn't finished shrinking yet, I let it go a little smaller than I want and then soak it in water for about an hour before I mold it. It soaks up the outside of the cast and it evens out the features because it dries from the outside in, of course. In fact, even after it's completely dehydrated, you can re-soak it in water and it will swell back up over a few days time. It doesn't seem like it matters how old the cast is or how many times you do it, it still swells back up.
Good luck! I hope my ramblings help in some way and I'll try to help if you have any other questions.
Andrew
