weee This is a difficult question to answer simply, so let me start start with how people control the face using the current Spine functionality. Check out the following thread:
https://esotericsoftware.com/forum/d/14304-portrait
As OatmealMu showed in this thread, some people use bones to create a frame that indicates the limit of how far the control bones can move, and then move them within that frame to create a sort of pseudo-joystick. This can be done without using constraints, but only with meshes and weights.
However, Spine does not allow you to create a rig that automatically switches the active attachment for a particular slot when the bone is at a particular position or angle, nor does it allow you to automatically change the order in which slots are drawn when a bone is at a particular position or angle. So for such major pose changes that require changing attachments or changing drawing order, the recommended workflow is to create an animation to store the major poses, and then copy the keys from there to use when other orientation changes are actually needed in the animation. This workflow has been the subject of several Twitch streams:
https://esotericsoftware.com/spine-twitch#video-WVLZCfitpdE
https://esotericsoftware.com/spine-twitch#video-FPaqO0Xlh4w
https://esotericsoftware.com/spine-twitch#video-7-xPu1y-Sp8
However, this approach tends to be difficult to manage because there are too many attachments to switch, especially in complex skeletons. In fact, we have received feedback in the past that they would like to see something like a slider or joystick to make it easier to manage. The following thread may be of interest to you:
https://esotericsoftware.com/forum/d/25654-request-new-timeline-constraint-linking-art-and-animations-to-bone-positions
I hope this will help you.
