Learning to work with a rotary tool
You've got a local makers DIY shop, so that is probably your best bet.
If it's current membership don't focus on crafts, just ask the leadership if you can start a craft night.  Volunteer to teach people how to make that walnut jewelry box during the first meeting.  Then at the end of the meeting, ask for other presenters to teach on other craft subjects.  With a little luck, you could build a thriving craft community very quickly.  Somewhere in that growing community, you will find the rotary tool teacher who can help you master it in an orderly fashion.

Beyond that, the best way to master a tool is to use it.
Find tasks which need doing where your rotary tool can play a part.  Then research on YT how to apply the rotary tool to that task.  Each new task completed increases your skill with the tool and in a surprisingly short time, you will have more new tricks to teach to your growing craft community.