People are not makeing a true corn mash on youtube.
They are just adding corn to a sugar wash and calling it shine. The corn just sits there.
Here is a shortcut to get shine from corn.
Adding a little bit of wheat germ can also help with the process.
1 part corn syrup
3 parts water (refill same bottle 3 times)
Add activated yeast and let it sit for a week in a container that can breath

If you’re ready to make a real corn mash from scratch, click on the link below