I came to Rhino around the launch of v7 - learning was on-the-job so-to-speak, driven out of necessity/exasperation with Solidworks and certain difficulties it presented to rapid prototyping needs. (Had been Rhino-curious for years, but it was the pandemic and lockdown that provided the opportunity to actually dive in and learn the ropes).
Learning outside of an instutional setting, and without real-world access to anyone who had even heard of Rhino - the most helpful resources were videos that are accompanied with insightful narration/commentary mainly the official McNeel Youtube channel, (and Vimeo, I recall at the time that many useful videos where there exclusively) - and certain videos from skilled users like @sgreenawalt (I happened on these early on when they were way over my head, but have returned time-and-again more prepared).
And I donāt know where I would have picked up the nuances (and massive value) of sub-object-selection technique without watching @theoutside 's tutorials, (the pen, the sharpener, the goggles - these were foundational!) - and this is now my main workflow where Iām working in dense, tight geometries.
Thereās a world of difference between videos that simply go through a sequence of steps demonstrating how to accomplish a goal, and those that contain a meta-narrative about āwhyā certain tools and methods are used. This goes a long way to developing a coherent context in the students mind, about the relative significance of different tools/features/approaches etc.
Other main learning resource being this forum of course.
Overall I found that gaining insights into the underlying structural nature of Rhino to be somewhat elusive, at least at first this was an unrecognizable obstacle that I bumped into quite a bit. (This has gotten better by the way, and the fact that that is even possible is a testament to the richness of the resources available, both the helpful humans and documentation and vastness of the possibilities of the software). I have some theories as to what this could be about.
Thereās a tendency that can be observed with software of a certain age/depth/complexity to accumulate tools (at later phases of development/sophistication) and features that go beyond the initially conceived logics and structures of the originating paradigm. Usually this is a great thing, and a response to user wishes, and developer ideas about what is possible/useful. Sometimes new tools blend seamlessly with the existing flows, other times they come with lots of special-cases and caveats.
The trouble occurs when newcomers are not able to discern, (or even be aware an issue exists) - when higher level tools and functions are mixed together and presented in the same toolbox as more fundamental tools. A large part of the backtracking and fumbling around that Iāve encountered had to do with attempting to understand why different tools like Booleans and Fillets worked strangely. Learning (from here on the forum) that things like Blend (iirc), and (maybe) Match use Sweeps under the hood was helpful in developing this situational awareness. Hearing long-time users decry certain tools as being less reliable for āreasonsā - but not offering any explanation tantalizingly suggests that there might be some merit in discovering which tools are more fundamental in the historical development. But this is relatively undiscoverable without being able to access earlier releases.
I suspect thereās also a tendency to want ālove all our children equallyā and not want to relegate more newly developed features to a different status, but perhaps some indication that certain tools depend on or reference the structures of others could create a compounding effect in accelerating learning and insight-development. A hierarchy of fundamentality is what Iām hoping for - Iāve purchased some of the early Rhino textbooks in the interests of plumbing these historical questions, (but for now theyāre still on the shelf!).
My uses of the software are for product/industrial-design, small-precision features, developable surface extraction for multi-material rapid prototyping, organic surfacing and mold-making, so for me the surgical qualities of the environment are exactly what Iām after.