Everyone seems so crafty. some suggestions please!

I need some advice from people who obviously know how to make things work and are better at figuring things out than me.
I have some clay pots that are a real pain to have to water,water,water in this Texas heat. So I thought that if I painted something on the inside of the pot to kind of seal them, they would hold water more like glazed or plastic pots ..But I don't know if this is a good idea and what kind of product to use. Any ideas? thanks! nancy