Hexagon shares allot of tools, and methods in common with many other 3D modelling applications, so its possible to follow pretty any training if you try to look at the method behind the tools, and not just at the tools themselves.
Character creation falls into use of many different mediums, concept art, concept sculpts, Game for low poly, or high poly characters, Cinematic. There is realistic humanoids, cartoon, creatures, and even although all of them share most of the same methods to create them, you still need to be targeting its end result usage. The reason why you don’t normally find a Tutorial on modelling the whole character is there is actually a huge process to it, that goes beyond just modelling it.
Anatomy is one thing which is a huge subject, and so important for more realistic humanoids. Just the Human head is a subject in itself, its so expressive, can produce so many expressions, so must be made to suit what your aiming the character to say for your animation, if anything at all. Because all character come with different clothing, there is a new flow of topology involved, while retaining good loops for deformation.
All the best.