Black out a portion of the screen

I’m trying to make a screen recording but want to ensure that some personal information does not appear in it. For example, it could be my username in the menu bar, or a portion of an app which has a picture in it. I don’t mind if that portion is blocked for the entirely of the recording.

Is there any way to overlay a black box or some image on the screen to block out some personal information in my screen recording? I am trying to do it beforehand so that I don’t have to edit the recording and redact the information later.

I tried using Preview, but when I interact with other applications, it falls behind the application window I’m trying to redact.