I’ve actually had pretty good luck doing my own drywall patching so far. I’ve learnt three significant secrets:
- If you’re not a pro, you have the choice between doing a slow job or a bad job. Naturally, the former is by far the better choice. So expect it to take a while. Applying the mud isn’t easy and will take some time for each coat. Often, you’ll botch it right near the end and basically have to start over. That’s OK, you’re not a pro. Just try again. Moreover, don’t think you’ll get things finish-ready after feathering out three or four coats; expect several more touch-up stages. Expect to do a fair amount of sanding. It’s taken over a week for me to complete each patch (largely because I have to wait at least 24 hours for the mud to dry between each stage).
- With practice, you can learn to remove mud and leave a decently-neat surface. By contrast, it’s virtually impossible to apply mud neatly. Even the pros don’t attempt that. If you watch a video of someone finishing a drywall patch on YouTube, you’ll see that what they do is apply significantly more mud than is needed at each stage, then carefully remove the excess to leave a neat surface.
- One of the most difficult patches is an interior 45-degree corner. Unlike 90-degree corners, they tend to be gradual and not sharp. Not only are there no tools out there to directly form such corners, trying to form one freehand with a straight knife is (by contrast with a sharp corner, which is tricky but doable) virtually impossible. The solution is to make your own tool. I used a piece of thin, stiff polystyrene cut from a salad mix container lid. I took care to cut one edge as straight as possible, then curled the plastic as I held it, making a gradually-curved edge to use to smooth the mud and make it match the existing corner curvature.
- It’s also exceedingly difficult to match texture. It’s noteworthy that many pros don’t really attempt to: their solution to patching a textured wall is to sand and retexture the entire wall. But I took it slow and blew a good chunk of my can of texturing compound just fine-tuning both the texture setting and my technique (I textured scrap cardboard cut from old boxes). While my two completed patches don’t match perfectly they do match closely enough that I basically have to know where the patch is and get a foot away from the wall to discern the difference. That’s good enough for me.