Try using a sea sponge while it is damp but not set, blending the edges to smooth taper (no sanding). I first coat, paper tape, coat over the tape, both with the same mix of 20 min. This coat should be thicker than drying type coats as you are doing one less step. Feather the edges with the blade, again, before it sets. Mix more 20, but thinner, feather edges and fill any remaining lows, follow immediately with a squeegee or knock-down blade (bigger to level better), no third coat, not required or needed if applied thick/smooth enough. Bend your blade to create an arc or use a trowel with a camber from the factory and a hawk. Wipe with the wet sponge as it is setting, just after cleaning mud pan/tools. Takes some getting used to, though it is very quick.
Gary
Gary
