Using a Wacom tablet with:

* A drawing app e.g., OneNote or Sketchbook or Krita

and

* A screen sharing app e.g., join.me

Has worked well for me. What's particularly nice is that you have a saveable, shareable, modifiable artifact when you're done with the remote session.

I'm also a bit surprised that Wiimote whiteboards never really took off: https://youtu.be/5s5EvhHy7eQ