I found the enamel paint at the craft store. (I used "Americana" GLOSS ENAMELS)
I painted some baby food jars and my thrift store cookie jar.
I used masking tape on the jars, but the lines weren't super clean. I'm sure it was better with the tape than without though... It took MANY coats and LOTS of drying time.
Pinterest told me to "fire" them to make the paint more durable. When they were dry I put them on a cookie sheet in a cold oven, set it for 325, and set the timer for 30 minutes. Once the timer rang I turned off the oven and left them inside for another 10 minutes then took them out and let them cool completely.
I love how they turned out! Happy crafting!