

One thing that someone that did it for a living taught me was to use way less than you think you need on each coat. Just barely cover it the first time, then knock off the high points before subsequent coats. You don’t have to get it done in one coat, and if you try, the result will be terrible and take a lot of work to get back to try again. And only do one side of a corner tape at a time.
He’s just shitting in the punchbowl, ignore him and hell play himself out.