Here's the recipe I used:
2/3 cup milk powder, ground (will grind down to ½ cup)
½ cup powdered citric acid
1 heaping cup baking soda
1 tbsp powdered cocoa powder
1 tsp sweet almond oil
Mix all ingredients well by hand, spritz lightly with witch hazel and pack into molds. ***
Now my experience was that I was able to unmold right away and then wrap tightly in Plastic wrape right away. I've used them and love them!
HTH