Fade/Blend one video through another

I am self taught and have run into a wall here...  I'm working on a project that has multiple videos on screen at once (they're all at 33% and I can see them all at once).  Several are "behind" the others and I'd like to "fade" them through the othe videos to the foreground.  I'm using changes in opacity to get the fade in/fade out and I thought that if I "cut" the video that's behind the other when they were both half way through their fade process and moved it in front of the other it might be smooth, but I'm getting a visible "pop" when that move happens.  I'm attaching a sample of what I'm talking about.  Can anyone help me?