Download for fullsize. If you have trouble reading my writing, comment and I'll decipher for you.
I don't know how much this will help, but I thought I'd give a bit more of a detailed description of how I work. I also found this was something that I struggled with a while ago, so I figured maybe it may help someone.
This was done in GIMP, but will work just as well in Photoshop, with a few exceptions that shouldn't be too hard to figure out.
Texture used: [link]
Reference for Castle: [link]
Thanks all, if you have any questions, don't hesitate.