Not only used on go-bar decks, but when I worked for an acoustic guitar luthier he had a radius dish with sandpaper glued to it setup on a machine that spun it quite slowly (around 120rpm or so). I actually did the bracing and body assembly while working for him, and I'd stick the assembled sides in the mold and carefully place the assembly in front of the sander and apply even pressure, checking often. This sanded the exact same curve on the edges that the go-bar deck put in the braced back.
With the tops, a very slighlty curved go-bar deck dish was used, however a flat sanding dish was used with a small wedge jammed in between the mold and the sides at the tail end of the body on the front side. This caused slightly more material to be taked off the end edge area, so when the wedge was removed a slightly curved/radiused edge surface near the end was achieved, to give the top a more 'domed' shape as I recall.