Many recipes call for the use of a non stick spray for baking dishes, slow cookers, etc. The most common would be PAM. PAM is mostly canola oil and some other ingredients that will leave a reside on dishes.
You can make your own cooking spray, which is done by many chefs, all you need is three items: a food safe spray bottle, olive oil, and water, that is it.
1 part olive oil
4 parts water
Shake and use, it is just that simple.