I'm not a scientist, but there's a similar issue in high tech. Back when I was in that world, I got training on public speaking to large audiences.

1) have a presentation, with the major points, but no details (about four per page)

2) try to stay in "the box" (an area to your right of the screen)

3) use your left hand to point up to the item you are discussing (most Western folks read L to R - this arrangement lets them make that same motion between your face and the point on the screen). No need to keep your hand there but give 'em a minute to figure out where you are on the handouts. (Note: you don't need more in your notes than the points to hit - best case is that your presentation is all you need)

4) for a big audience, use larger than normal gestures

5) rehearse

I went into this having no problem explaining tech stuff to audiences of 25-200 - but add a zero or two to that, and it gets daunting - and qualitatively different. I had one presentation (maybe 5K people). the tech demo went very wrong. Threw my hands in the air (hey, big gestures) and got a fairly amazing roar of laughter from the audience.