I have a shot where a stationary guy is getting sprayed in the face with a fire extinguisher. The actor knows it's coming so he blinks in the split second before he's sprayed. Can I make the pixels from the open eyes, stay where they are in the frames that follow, so that the closed eye pixels are covered with the open eye pixels?
Roto the eyes so only the eyes are visible, set an in and out point just before the blink so the eyes stay open, move the layer in time to cover the blink.
If the camera moves or the head moves you have to adjust the position and maybe animate it. That's all there is to it. Layers and time shift.