Here’s another method you could try:
Make a pre-comp with all expression artwork layers sequenced back to back.
In your main comp, apply a “freeze frame” to the pre-comp at the timecode of whichever expression you want.
From there you can just add new “hold keyframes” at new time-codes whenever you want a new expression.
I’ve attached a couple of example screenshots incase my instructions are confusing.
Expressions Pre-Comp:

Main Build Comp:
