If the tutorials people posted above dont click with you then maybe try these, i personally found this stuff very helpful when learning about materials and hand painted textures.
The links and help above though is good and if it helps you great!
I found allot of this complicated when i started since i am fairly new to Photoshop so i did everything in stages, all base, all cracks, all highlights on a separate layer ect.
<-- this was a big help to me! his damage reads really well.
Hope some of this is helpful to you!
Really love Clive by the way so gogoogogogogoogo! Can't wait