How do I use craft paints in a spray bottle?

When I sprayed painted my terra cotta, I just used the spray as is. I did not dilute it.

Water. If craft paints are acrylic. Cleans up with water.

Here is a tutorial showing how to make spray paint from craft paint.

https://www.instructables.com/id/DIY-Spray-Paint-2

I think that using acrylic paints watered down with water isn't going to give you a very good finish on your pots. The paint will be thin, fairly transparent, and more than likely will wash off your pots very easily if it even adheres at all. You don't say what your pots are made from but I think you would have better luck with a regular can of spray paint.