A few years ago I worked on what was supposed to be a "short film" but really just turned out to be a vanity project for this model that wanted to try writing and acting (she couldn't do either). After shooting less than half of the script (which wasn't that long. About 20 pages if i remember correctly) she took all of them money from the Kickstarter to pay for photoshoots. She claimed they were for "promotional purposes" but that's not what that money was for. That money was given to you to FINISH THE DAMN MOVIE! Long story short, she misappropriated funds and becase of that this short will probably never be finished.
This has less to do with the technical aspects you're asking about but something to keep in mind: if the performer is going to be singing in the video have them actually sing the way they normally do while shooting. You obviously wouldn't use that audio but if you just have them silently lip sync it will look odd and fake since certain muscles in the face and neck wouldn't be moving they way they do when someone actually sings.
What if you have no intention of producing or even distributing the screenplay? I want to adapt one of my favorite novels as a sort of writing exercise but have no plans on showing it to anyone. I just want to get better at formatting and screenwriting in general. Any tips for rewriting the work for the screen?