Old fashioned texturing

First of all I’m not going to even consider if it’s worth to learn old fashioned texturing techniques and its pragmatism by simply relying Photoshop or softwares like Photoshop in order to achieve realistic results. Given all this I was wondering what tutorials did you guys as beginners and or professionals have found the most valuable and information worthy of purchase.

In case I wasn’t clear enough I guess I should clarify a bit more what I’m looking for exactly. I’m looking for tutorials of any format that will If I’m dedicated and patient enough enable me to learn not just how things are done in texturing world but also why are they done that way, in other words I want to learn about pragmatism and the technical side of texturing and not just repeat what the author does without any explanation and thus not learning anything as a result. Before you guys direct me to 3D Coat or Substance Painter keep in mind that I’m completely aware that those softwares are the industry standard nowadays (especially Substance Painter) but I’m pretty sure that in order to use those softwares in the most efficient way with the most stunning results to the best of ones ability you simply have to know the thought process behind making each individual layer of your object as you are texturing.

All in all I’m trying to say for the third time is that I don’t feel learning old fashioned texturing is a time wasting activity but rather an extremely valuable experience that will prove really useful and transferable when it comes to texturing in other softwares 2D or 3D alike.

Thank you in advance.

However, I will accept reality that Substance Designer tutorials and reading materials provide pretty much there is everything to know about the theory of creating textures. Since you have to have an extensive knowledge of materials, colors and textures in general in order to work properly in that software, am I right or am I wrong?