It seems to me applying your advice takes much more time than one can spend on preparing a presentation ! For most people, the issue is not to prepare a conference for hundreds of people but a presentation for a group of 10.

Practicing aloud seems totally artificial. It is not that hard to imagine how it will sound. You can do it mentally while re-reading and editing slides.

The hands-up trick at the opening of a presentation is something that needs cultural adaptation. In France, it feels very "american" (which is not necessarily negative overall but in this cas means "superficial" or "artificial"). I'd suggest something more subtle, like referring to something someone just said before the presentation, something that feels more improvised than prepared.