just some ideas from various things i've seen in various places
if they shell up to protect their face, you have some options
1. trap hand, peel, and punck/elbow/knee
2. body kick or low kick
3. angle off to the side (marvin cook vid)
if they stand in place to do head movement
*i already had the idea to hit body or kick legs but i wasn't executing because i think 1. i was too far away or 2. off balance
*per marvin cook vid, trying to punch head while they are standing in place doing head movement is a stupid game. its stupid for him because what he needs to do is move his hip/entire body away from you. otherwise, it's just a target. its stupid for you if you keep trying to chase his head because he's able to defend from that specific distance.
*what you need to do is take a step or half-step in, then punch either to head or body