All recommendations are welcome. In particular how to vibrate a two part mold without it breaking apart. I did not weigh the mix and water, but i suspect i used too much water. Also added about 2% plasticizer.
Both good options. Don't need to be fancy, so long as it works.
Re the vibrator recommendation - that's hilarious but apt. You want something that doesn't move a lot, but oscillates a ton. A vibrator fits those requirements. A mechanical toothbrush could work in a pinch, but you don't want the rotating toothbrush head, it's the motor vibrations (offset? Can't remember) doing the trick.