it sounds like you need a gimbal mount of some type, kind of like those gimbal chairs used for astronaut training that have 3-axis motor control. another solution would be to have a robot arm and a table, and the robot arm grips one pair of sides of the object, and (assuming an object with flat sides like a cube) rotates the first four free sides to the polisher, then puts the object down, rotates, and picks up the object by two sides that have already been polished, and applies the two remaining unpolished surfaces to the polisher. that's probably much simpler than controlling a gimbal.