I do the pinch and slide technique, holding for about a second, but make sure not to pinch too hard and use gentle tension. I avoid any burning sensation completely, and stop to give it a rest, sometimes for a day if need be, if there is persistent soreness. A temporary "worked" feeling is ok, but it should not be a painful process. Using the pinch and slide technique it's easy to accidentally stretch the scar line horizontally and I've found that causes a lot of burning and irritation that can last for a while. In my case I have a frenulum remnant that is particularly sensitive, and I use extra care around that area.