About two weeks of four hour days. Perfected my approach about half way through so had to redo it. Feels Good Man Approach currently is - Tape it. Then put a light coat of 20 minute mud over just the tape. Re-expose just the corners of the tape. When the 20 minute spackle dries, sand it down to *just* above the tape. Use the exposed tape corners to know how far it is currently off. Now use a 12” trowel to taper off the tape (or 8” for corners) and 45 minute mud. The dried spackle over the tape will provide a perfect guide for the trowel to make a perfect ultra low profile taper. After this do a flattening pass with a 12” normal blade in the direction perpendicular. This is an on off pass which serves to flatten in the other x or y direction and provide a smooth covering. Done with normal bucket mud. After this spot fix streaks and holes with bucket mud and a 4” blade. After this it should be flat and smooth already. Two even passes with a sanding sponge with the purpose of smoothing not shaping.