Interesting. I actually use this technique on pain fairly regularly, and have found it works well. I've always mentally modeled it after Dune: Feel the pain, acknowledge it, and let it flow past me.

I've also found synaesthesia useful, although I may be unusual in being able to induce and control it - modelling pain as colors, or converting it in to a pleasant sensation is quite useful, and I've found I get better with practice. My body will often have about the same involuntary reactions - flinching, yelling out - but the emotional experience is quite different, and I can take quite a lot of pain without feeling terribly bothered.

It might also help that I've had some extremely painful medical situations, and didn't have much choice but to learn to deal with it ^^;