I've been using homemade cornstarch for years.
You can adjust the recipe if you want thinner or thicker.
This will give you a fairly stiff fabric.
1/4 cup corn starch
1/2 cup cold water
1 quart boiling water
Dissolve the corn starch in the cold water then add the boiling water.
Stir and let cool before use. You need to give it a stir every time you
use it so the starch does not settle down. I use a big paintbrush to
apply the starch to the fabric. Hope this helps.