dear Puddingbowl,
Still thinking autonomic nerves, I would say it is possible you have irritated the vagal nerve in your enthousiasm.
I will get back to how to treat patients with this bindegewebsmassage in a while.
Still afraid you cannot learn this online though.
AND I am an old bird, and Cyriax trained but NEVER EVER do I mobilise or passively "treat" the cervical spine anymore;certainly not using the old Cyriax´s "techniques".
Esther