Remember that if you're on an open diff, you may only "shave" one of the two rear tires... if they're directional, you may have to spray some water (or do something similar?) to get the other wheel (the one you couldn't manage to spin) to 'shave'.
If you have non-directional tires, you can swap 'em around as you please... just make sure they all get 'shaved'.
If you have an LSD (or even VLSD) you won't have to rotate the tires as much.