If you’re in a rush, start drawing a thing or writing a word and give yourself permission to move on before it’s done. Then go back after the presentation is over and fill in the missing information.
As long as you have a clear idea of what you need to fill in and you actually do it, you’re all set. This method is also great for times when you’re not sure how to spell a word or a name. Write the few letters you’re sure of, then go back later and fill in the rest.