Hi Sid,
You might not be able to find a very Course, that teaches you a very specific thing. But: “…the fundamentals I need to do something on my own from scratch”
Being able to re-topologize a creature and looking at existing basemeshes of humans, should get you there already. A few hours of studying re-topology, might not be enough.
If you are good enough at modeling, you can model a bicycle, even if there is no “bicycle modeling” Tutorial available.
And that Course on YT I linked to, does the whole body, not as a re-topology, but that was not what you were asking originally.
