>>105993721i should also lead with the idea that VRC does not hold your hand when it comes to integrating face tracking at all
some booth creators will sell addons where you can sloppily patch a model with face tracking since most don't come with that stuff set up but its a real pain in the ass especially if you like to take your models into Blender yourself since the patches aren't designed to work whatsoever with anything but the base model prefabs
if they allowed native SDK integration or a way to set visemes to dropdowns that'd be much nicer than the fuckery required currently
eyes can be default enabled with a subset (simultaneous blink and X/Y rotation) with any OSC eye data so that part can be done for all avatars without extra faff
if you want full individual blinking, pupil dilation, etc. you'll need to do the same fuckery as face tracking for each avatar