Weirdly enough, that is a subject I have not had much opportunity to teach on. One time when I was able to do something related to teaching geologic time, I used a long rope with knots tied at certain lengths to represent the different eras and major earth events. I had kid come up to represent the beginning and then I had each other kid start at the beginning and walk along the rope until they hit a knot. I would explain the event and they could visualize the length of time between events. I got the idea from another Australian geologist on Instagram, but I can’t remember their account. It was a few years ago I did this, but from what I remember, the kids got a kick out of seeing the length of time humans had only been around in comparison to the rest of time.
In my limited experience, visualization has been the key. In the Alf museum tours, our docents have the time spiral in the front of the museum created by Raymond Alf. The time spiral is colored coded to show the different eras and has labels on major events as well. The very tip of the spiral shows the appearance of humans. It seems to do the job here.