orry for not answering, and, yeah it was a lot because I learned by copying and watching, not the fastest way , and shading?, I have problems with that, but I think that once you understand how lightning works it should be easy, or use 3d models like the ones in CLIP Studio, or easy poser, or have a lamp and a posing doll, if you're talking on how to do the shading, there are many ways, there's "hatching" that is with a fuckton of lines
Or softer ones, or more intense ones that give contrast
The first step really is doing squares, lines, dots and circles, but that's mostly so you can get comfortable with drawing, or if you really have never touched a pencil or brush and also to get good with your hand pulse.
It can be both really, some people just can do shading without prior training, most of us, don't, and more than "skilled" is as I said earlier, grasping the object in your mind, and its dimensions, or using references and/or models to help you with it, either way works.
Also each type of shading might be easier depending on were you are doing it, I think hatching is way easier on paper, but smooth shadows and blacker ones, are easier on digital.
View: https://www.youtube.com/watch?v=K7DseLvcpyY
There are a lot of tutorials on how to do so like that, it really depend on what you're trying to do.
Good luck with your goals