This is a great question and unfortunately the hostility here and from your friends is an omnipresent, shortsighted thing. These tools are very powerful, but quite finicky.

I haven't found any particularly good courses, however I do enjoy this YouTuber, who covers Midjourney and some other generators:

https://www.youtube.com/@WadeMcMaster

The key thing you should try to do is this: make them understand that genAI is a toolset, akin to Photoshop.