Since this is mostly a Lachlan Giles fan page, let’s start with his entry into X guard:
He has good tips for controlling the position and keeping your opponent’s posture broken down. The entry involves altering your butterfly position a fair bit. You’re abandoning the butterfly sweeping position. What if you’re already committed to the butterfly sweep? I like this version that puts the transition right into the failed sweep:
Once you’ve gotten that far, then what? Stephen Kesting’s summary covers several options in a nice, succinct video:
I think this one moves a little fast for an instructional, but if you really want to taunt someone with your awareness of the matrix, this back take is fun and so is the ham sandwich at the end: