Working in a paint department, spray paints are pretty much self-service as anyone can easily grab it and go. However some places do custom make spray paint but it's rare, and I heard they have their own shaking machines for them even though I haven't seen them with my own eyes. I had one guy one day that insisted we had one of them which we didn't. He didn't want a custom color in a spray, he just wanted a factory-made spray-can shaken via machine. I told him it didn't exist at our location and he said "how am I suppose to shake it?" like he was the most incompetent person in the world. I really wanted to wave my arms around making a face. That's why they have the little ball, it's not exactly rocket science or tough labor to do it.