What are your routines at a delivery presentation? How do you deal with presentation anxiety? How do you ensure that all aspects of the product are covered? How do you potentially fix aspects which are lost, which you forgot/missed to cover in the presentation?
As you gradually get better at it, you might skip the drugs and do less preparation. The thing is, at least within a single job, the presentations revolve around a set of subjects and with time you will just master talking about these subjects. That's how managers do it - their jobs are pretty much mostly talking, so they get a ton of experience quickly and become very competent at presenting and discussing relevant subjects.
The dry run helps me get used to it and lower my anxiety. If I still feel it by the end, I will practice more, and really try to imagine that it is the real event with the real folks watching me.
Then practice again.
Many people think they can wing it because other people can wing it. The secret to their winging it is that they practiced it 100 times beforehand.
Practice.