I do know some people who use Powerpoint presentations, but it seems like too much work to get them together for me.
If you have FI course notes / diagrams from a book and know your material, then take care to build the diagram up one layer/important component at a time on the whiteboard - take some care with the actual drawing but the whiteboard should be a backup to what the student has learnt in textbooks so as long as the two can be related and you clearly explain each bit I've generally not found it an issue.