You need a tapering tool for those butt joints ,i use a grinder. Its that or feather it out a foot or more in both directions. Some jobs are much worse like blowing insulation in summer.I've got the tools. I have been doing this for years. It just gets less fun each time. A few years ago I was in a hurry to get a project done. I hired a couple of guys to mud and tape. A year or so later they were at the house. They remarked on the how well they had done a butt joint that you see as soon as you open the door. I told then it looked good because I had redone it after they left.
I take grinder and put a taper on the butt ends just like the factory taper. Only diff is it no longer has paper on it unless you count the tape. THey also sell a machine to do that,kinda expensive though. Another method is to place the butt ends between joists and place a tapered board behind which bends the ends inward but that dont work as well for me. Screws tend to pull through,i just did one like that, ill have to take a picture of it. I didnt mud it yet.Explain please. I take a knife and cut a small v groove between the screws, pack that, and start taping.
Classic mistake. The more you work it, the worse it gets. Same as Concrete .Like anything else, practice makes perfect though.I had to build a chase around some new ductwork and wires in a bathroom. Rocked and stared mud this weekend. I am NOT good at mud. I always think I can smooth it out just a bit better to make sanding easier and end up Making a mess and having to redo it.