A fascinating video - ‘Behind the Scenes of Star Wars: The Original Trilogy ILM Special Effects Makers’:-
https://www.youtube.com/watch?v=85MK2GDkoxo
a 1 hour documentary focusing on the people at ILM doing the special effects for the OT movies. Try not to let the length of it put you off, the video flies through the time and leaves you wanting to know more! 😃