Most pony plush makers almost aggresively hide all their sewing secrets and patterns, keeping everything for themselves. (their FAQ's almost shout "no, I won't say anything!")
However, the best one in the crowd, adamlhumphreys (https://www.deviantart.com/adamlhumphreys) decided to share his secrets and tricks he uses, including a pattern for a pony plush.
The pattern, with files, vectors etc. can be found here:
the files are in the 'download' section for a mere 250 deviant art points (like, 2 dollars).
But if you, like most of us, don't know what to do with such a pattern, then you can watch YT tutorials uploaded by adamlhumphreys (https://www.deviantart.com/adamlhumphreys) so you can see and learn.
this is the