Why does my corner bead flange still show after multiple coats of drywall mud?
You appear to be approaching this in a scattershot manner and expecting too much, too soon.
Odds are also great, given the foregoing, that you are overworking the mud trying to get it perfect (yes, I'm guessing.)
General mudding procedure anywhere: grab your narrowest knife, put on mud, stop.
Scrape off any high points, grab your next widest knife, put on the second coat, stop.
Repeat until you are at your widest knife and/or it looks good enough. If you have so many knives that this seems absurd, set some aside to make a reasonable progression (4, 8, 12, etc..)
Realities - mud shrinks as it dries. So, if you spend a lot of time and effort getting a perfectly level surface - it won't be when it dries, until you reach the point that you are only putting on a very little bit to fill the shrinkage from the previous coat, and it wasn't much shrinkage. &quot;Hot mud&quot; shrinks somewhat less, but requires mixing only what you are going to use each time, as it sets up rather than just drying out.
So if you are getting bent out of shape by the state of things on your second coat, you are approaching it with a very unrealistic attitude, and you'll be frustrated. Just accept that it takes multiple coats, and you'll waste a lot less time putting coats on &quot;perfectly&quot; if you realize that you're going to scrape or sand off any high imperfections, and fill any low imperfections on the next coat. Then the job becomes mostly waiting for it to dry so you can get to the next coat (and don't skimp on the dry time - if you are in a huge hurry, use hot mud.)