I use several free hand hollowing tools, including an old one from Sorby and a couple of Hunter swan neck tools. I just bought a set from the other John Jordan but haven't tried them yet. A lot of people do a lot of hollowing with these, all by hand. He does sell a handle with forearm support if you find you need a little extra support.
As mentioned, you don't need a rig for hollowing. Working freehand is a bit more effort to get the thickness you want. However, some good calipers and some patience works every time.
JKJ