I think Walter’s split-screen idea is probably a lot easier than messing around with Green Screens.
The problem with split-screens is that you can usually see the line. Doing it outside only adds to that problem because the sun will probably change slightly between takes. If you’re using manual iris you can sort of adjust, but it won’t be perfect.
The solution is to set up your shot in such a way that there are natural lines WITHIN the shot. Place things on the ground like hoses. Use a tree. Whatever it is, just put something between them that you can hide a line on. That’s the key to making it work.
Then, instead of doing a simple split-screen, export a frame to Photoshop and make a mask. In other words, make an image that is half black and half white, each representing half of the scene. If you do it this way you can draw a very compicated line that goes all over the screen. Save that b&w image.
Then, in Final Cut use the “Image Mask” filter and drop your B&W image in it. You’ll figure out how it works pretty quickly.
Take a look at this example, I’ve put the finished video here, and if you scroll below it you’ll see what the mask looked like:
https://www.redfeathervideo.com/kirk/
Notice how the mask goes down the edge of the wall and along the pattern in the carpet? That helps hide any problems with the mask or any lighting differences. I shot that back in high school and did it on my old Adobe Premiere 6 on a G3 iMac. So it’s not a very complicated trick that needs much horsepower, that’s for sure.
You might want to try something like that, but no matter what you chose, TRY IT on your own time before you actually shoot something that matters. You’ll learn a lot the first time you try something like this, so do it on something that doesn’t matter.