From the Bottom Escapes section of BJJ Foundations with Cal MacDonald and Stephan Kesting https://www.grapplearts.com/bjj-foundations/

Five essential movements required for butterfly guard that can be trained as solo drills. Partner applications also shown (see timestamps below)
00:00 Intro
00:10 ONE – Solo Armdrag from Butterfly Guard Kata
01:06 Armdrag Application with Partner
01:41 TWO – Solo Butterfly Sweep Kata
02:36 Butterfly Sweep Application with Partner
02:57 THREE – Frame and Hip Escape Guard Retention Kata
03:42 Frame and Hip Escape Application with Partner
04:22 FOUR – Forward Situp (aka Butt Double) Kata
04:55 Forward Situp (aka Butt Double) Application with Partner
05:41 FIVE – Elevator Butterfly Guard Reset Kata
06:28 Elevator Butterfly Guard Reset with Partner

Good luck with your training,
Stephan Kesting

P.S. Grab my free checklist of BJJ positions and techniques here: https://www.grapplearts.com/book