How do you sketch on paper during a virtual (COVID-19) interview the working example for coding interviews (not design interviews)?

E.g., I typically work on a concrete example and sketch the data flow and indices in an array, data flow in the DP matrix, etc.

I do this for about 2-5 minutes until I get the hang of the problem.

However, if I do this in a virtual interview, all the interviewer will see is me looking down for 2-5 minutes and talking about numbers and indices the interviewer cannot see.

I can sketch on a virtual white-board. However, drawing numbers in arrays on a virtual white-board with a mouse is slow, which defeats the purpose quickly trying out things on a working example.

Do you use tablets (e.g., iPad) paired with your computer, to make drawing on a virtual white-board easy?

I don't have a tablet, so I am worried about glitches with connectivity between laptop and tablet (e.g., if screen mirroring), keeping my hand on the tablet's screen, etc. Which, during an interview, would make me run out of time.

I could experiment a bit with a tablet, but I don't want to buy one just to find out it is the wrong answer to this problem.

What is the experience of people who took such virtual interviews?

Thanks!

******* Followup based on answers to this question: *******

Thank you all for your replies!

Here are 2 good virtual whiteboards:

https://awwapp.com/#

https://jamboard.google.com

However, my concern is this:

I can sketch with a mouse on these whiteboards to communicate to the interviewer something (once I know what I want to communicate), which is good.

However, brainstorming and working on examples for myself (while letting the interviewer see what I am doing, i.e., that I am taking good examples and that I am moving in the right direction) is difficult to do with a mouse: because I am focusing more on the clumsy way of writing with a mouse (e.g., think how you would write the 10 20 50 30 77 with a mouse) than on my own brainstorming.

So my question is about the latter topic (brainstorming and working on examples for myself).

Any thoughts and experience from real interviews are is much appreciated!

Thanks!