How do you make a breathing animation? For example, after a blowjob the character needs to catch a breath, how do you animate this?
Imagine how a human anatomy changes when a deep breath is taken:
1- ribcage expands forward and up
2. posture straighens a little
3. shoulders go back a little
4. mouth shape / jaw opening size may change
5. for added realism, add nostril flare, eye open size
Most of these movements/deformations could be effected in a G3/G8 model with various sliders on the chest, shoulders, face, particularly if you have any of the body morph packages, and posture change with the normal bones.
For the sex act, presumably there would also be swallowing, licking lips, wiping away saliva.
The "secret" to realism is to be subtle in your morphs and ideally not make a simple one-breath cycle loop... real world has small variations in movements and position even if a person is trying to be as motionless as possible.