The plasterere I started out with always used to join the ceilings we did, could have had something to do with them being approx 80m2 and about 7 m high. We used to skim the boards and stop where the scaffold stopped, trowel off then cut it back with the trowel so that it was to the 2/3mm.
We would then work up close to skimming that was finished before and at the final trowel we would work it upto the other stuff and keep the edge clean.
I always patch this way aswell and the joints are invisible if you keep the existing plaster clean, this means washing down with a sponge to achieve the finished job.