Yah, but the other 5% want to know how to do it RIGHT.
It's tough to determine what is exactly right sometimes. For a Best Quality British or a very high grade American double shotgun many would agree that a perfectly timed custom made replacement screw is the only acceptable repair. The idea of perfectly timed screw slots is mostly a vanity thing reserved for higher grade and hand made guns. Quite a few manufacturers gave virtually no thought to screw slot timing on lower and mid grade doubles. You can find well regarded guns that have visible screws that are set in position with a smaller lock screw, where the head of the lock screw is inset into the perimeter of the main screw head, yet the main screw slot is not timed.
Early on in this Thread, someone said that the method of using a thin "shim" or washer under a screw head did not constitute proper gunsmithing. However, for the vast majority of field or mid-grade guns, it simply wouldn't make sense to pay a Purdey trained gunsmith to make a screw from scratch. The video that was posted separately on making a gun screw was very incomplete. It didn't show anything about selecting the proper screw stock, machining of the threads, or any engraving, or correct bluing or finishing. All of that work just doesn't make economic sense for the majority of guns, and most guys would be happy with a good used screw from Numrich, no matter where the slot ended up.
It is interesting to hear the various thoughts or methods available to accomplish the goal of timing screw slots, but for the most part, there isn't much new under the Sun. The idea of mixing cyanoacrylate glue with sawdust as a filler sounds very much like epoxy glass bedding. Rotted or punky internal wood has been replaced with Baltic Birch plywood, and inletted to fit. Same for pillar bedding to maintain spacing between top and bottom tangs. And the method of gluing in a small piece of wood, and then inletting to fit has been mentioned here by the Stock Doctor DES/TSD, and certainly wasn't invented by him. Some of these repairs might be a big disappointment if found inside a gun that was represented as unmolested and original.