Here's a tutorial that I made, that I'm now making it pay what you want/free. This tutorial contains a valuable piece of information that I believe will improve your texturing game! I start with a high poly base in Maya, export my maps, and finish the texture in Photoshop, by using a combination of hand-painting and photo-sources. Even if you are only familiar with Substance or Mixer, it really pays off to have this knowledge in your arsenal. I find myself jumping from SD to Zbrush to PS all the time to accomplish what I want, and it's very freeing to be able to do so.
If you enjoy the content, please take a few seconds to leave a rating on Gumroad. (Just go to the product page after you acquire it, and the rating option will be available). This will greatly increase the visibility for this product, and help make my page more popular!