You should be aware that "isotropic tumbling" is state of condition/motion in molecular chemistry, and not a mechanical process that can be applied to a gear of other parts? The polishing process, "tumbling", will also not induce such molecular activity in parts so treated, either.
In any event, tumbling or otherwise polishing only the gears won't do much to improve shifting, since the gears themselves are seldom the main source of the friction that impedes it. Only the splined centers of the "sliders", the gears that are moved along the trans shafts to accomplish the shift, and the splines of the shaft on which they move, can improve that motion by being polished. It does help some, but unless the shift fork follower pins and the interior sides of the shift cam are also polished, the major source of resistance would be overlooked.