About once a year I rejuvenate all my metal clamps with my biggest metal file. The back of the steel bar on the clamp becomes smooth from wear and the clamp don't grip and can even slowly loose it's grip when tightened. Not good! With a sharp edge on the file I rasp the steel bar. The clamp get's its bite back and will work as new for a while until the new scars and chips wears down. Can be done multiple times :-)
Having around 40 (rather cheap) clamps I don't bother to file each groove, I rough it up real quick with a sharp edge on the file :-) Probably better to file each groove with a needle file but that's a lot of work.
well yeah, like the most basic, obvious idea ever...
...that wouldn't have occurred to me in a million years!
I agree, not high tech. But still something that even at least one seasoned guitar repairman I know didn't think about. Sometime it's the simplest things that eludes us :-)