So this is a trick that’s been out there, but something I didn’t know until my FC buddy, Bean, informed me of it yesterday. I tried it last night, and sure enough, it does work. Thanks, Bean, for making my breeding and trading so much faster!
All you actually need to do this is the Tauros mount, which you have before you get to the Nursery anyhow.
It also really helps to have your party lead by a Pokemon with the Flame Body effect. I wasn’t aware that having one of these Pokemon in your party means that the number of steps that you need to hatch a Pokemon is halved. For the Jangmo-0, that’s normally over 10K steps… so this reduces it significantly.
Two early options for Flame Body is a Fletchinder, which you can get from evolving Fletchling, or a Magby, which you catch in the Volcano trial area just a little beyond the Nursery. Again, this helps a lot, but is not required to do this trick.
The Tauros Trick
Now the idea is to go to the enclosed fence area right in front of the Nursery and while standing inside, mount Tauros. Then hold the B button down to make him do his rush move while rotating the direction pad in a circle. He will perpetually run as you do this in super speed, which counts towards the steps you need to hatch your egg.
For a visual on this, check out this video:
Hope this helps!