This divot took about a hour to repair, the disc is good, but you have to take your time and feel what the metal is doing. Smooth dents are fairly easy, crunchy dents (like this one) take a little more time. It doesn't turn the metal blue when you use it, like a torch does. You get a feel for how long to run the disc over the area and hope the soapy water seams when it hits the metal. You can let it cool naturally, but that takes a while. The metal will continue to shrink after you use the water. It's a neat tool. A little practice and you can get good results. I did not use any sand paper on this repair, just a piece of red scotch-brite pad to clean the wheel and to remove the residue from the panel.