Remove menu bar and dock from external monitor? I have a MacBook Air (10.13.2). I'd like to play videos full screen on an external monitor, while still being able to continue working on my MacBook.
I can't get it the way I'd like.

Whenever I click back on my MacBook, the dock and menu bar appears over the full screen video on the external monitor.

I've Googled and the only way I found to get rid of them is to uncheck the "Displays have separate Spaces" in System Preferences >> Mission Control. 

However, that brings the unfortunate effect that when I switch to a different desktop than the one where I started the video, I lose the video on the external monitor as it too switches to a different desktop.

Anyone know how I can get rid of the menu bar/dock on the external monitor and still keep it as a separate space?
Try setting your dock to autohide while leaving the displays with separate spaces. Also make your video playing app fullscreen before using the fullscreen feature built into the app.

This answer says that the menu bar cannot be hidden, but it shouldn't be showing up in full screen unless you place your mouse over the top of the second monitor.