… listened to a live webinar.

The presenter opened by saying, “Today I am going to try using PowerPoint slides to help me stay on track.”

That tells the audience two things:

1. I’ve never done this before.
2. I don’t really know what I’m doing.

Both may be true, but your audience doesn’t want to know any of it.

They want to believe that you are an expert and that the time they are about to invest is going to be worthwhile. 

Yes, your performance may burst their expectation bubble. But there’s no reason for you to do it yourself, before the fact.