Frame Animation - Adding An Object that Doesn't Start on First Frame - PS CC

Hey Guys - First post here, so let me say thanks in advance for your help, and your patience. I did a search in multiple places and couldn't find the answer.

High Level

I'm trying to figure out how to make a gif and add content to it in PS CC. I have figured out how to get a layer to stop when I want it to (by keeping it visible until it reaches the desired frame), but I'm having trouble figuring out how to add a layer that doesn't start at the beginning.

Detailed Description of What I'm Trying to Do

I'm trying to animate a gif of the Three Amigos Salute with different faces. Powerful stuff, I know.

https://giphy.com/gifs/sY1yvrxROgCM8

So I figured out how to add the faces (first faces). The problem is, towards the end, the characters turn their heads, requiring new "faces" (second faces) to layer on top.

I figured out how to make the first faces stop when the head turns. However, when I add the next layers with the second faces, they play from the beginning. I only want them to start at a certain frame.

Is there a way to accomplish this?

Thank you so much,

Jeremy