Something like AppZapper has a pretty simple process underlying it: it gets the application, the prefs, the cache, the widget and the whole ~/Library/Application Support folder for Skype. Frankly, I would think dragging the Skype app, continuing the example, would get that. Or you could do it manually.
The problem with searching as detailed in the video is if for some reason Skype has been used much. I got about two pages of hits: images, email messages, etc. With some boolean work I could trim that down further and further...but why? In the end I still had to decide what was necessary to dump. Some other applications, for example, had components that interfaced with Skype. I might not accidentally wanna delete those.
And try it with something that uses plugins; the application may have installed them, but you'd never find say the framework with tracing down the symlink in the application package itself. Or BOM files. Or prefs under other names. Fonts? Man files? You could go on forever.
But why? I actually think the safer route is to do as Apple suggests and drag to trash. Or use the application's uninstaller; the fact they might provide one is a hint that you need to use it. Otherwise, if what's left doesn't cause problems, ignore. Or erase your hard drive and start over if need be. A bad application (Colormunki once in my case) can be a nightmare to get rid of if it installs non-standard stuff that does cause problems; but there is no one way out of that; even searches won't help.
I have junk going back a decade on my mac that takes up a minute amount of disk space and isn't worth the time to track it down and do something with it. Maybe you have tons of free time, but if not, just throw it in the trash and see if that works.