It is quite a tricky process to make your textures entirely in Photoshop, though it is of course possible. There are other pieces of software which a lot of people use these days, such as Substance Painter, but of course these come with a hefty price tag.
I personally do a lot of the basic work in photoshop, adding details and highlights and such, while the actual texture comes from a texture library online. I personally was a big fan of textures.com, which provided thousands of seamless textures, but unfortunately they stopped allowing free accounts to download textures.
Ambient CG is still free though, and they have a couple thousand, free, seamless textures.
Using different layers with display types in Photoshop, you can take a single texture from one of these sites and use it to add texture, a layer of grunge, even use it as a mask to make chipped paintwork and such. I did that here, making a VERY basic texture in photoshop and then used one stone texture from ambientCG to add detail.
Unfortunately, in my case it was a case of learning Photoshop's features over a number of years and often times stumbling into an effect by accident.