Sander works well. Use a little polishing compound to clean up the area where you removed the NFHU designation. The S-12 tires have number, letter combos that are near pre-formed boxes on the tires. Unless the officer in question is well versed in DOT letter number combos you should be fine. I had a police officer look at my tires in a fairly close fashion when I did mine and his statement was "looks good to me." I did mine on a whim and am glad I did cause it would have cost me a set of DOT tires in order to pass inspection if I hadn't!