I mean how could he exactly pin point the exact location of the figures, Is he using any other inter faces ? or its just the video was recorded and the figures were added later according to his hand movements ?
Even though they have added figures after recording the vide, how could he maintain the consistency in pointing the previous figure that he drew ? Is there any technique ?
He's just re-acting based on pre-recorded footage using a control monitor and a live keying hardware...
AE BASICS: You can do that in post by simply drawing paths on the video layer and adding and animating Effects>Generate>Stroke or by adding a shape layer with a stroke and using trim paths. It is just a simple matter of lining things up and layers.
If you have more complex paths you want to follow you may need to do some tracking but tracking was not necessary at all in this example.