Adding white Tutorial

I was asked awhile ago to make a tutorial on how I add white to an image. Honestly...I completely forgot about it until I was adding white to an image I am working on. <.< Then I was like...CRAP!

So I figured I would throw one together while I was making it. <.< It's completely unfinished when it comes to anything but the markings{which I still might toggle with a bit}...but I figured you could see the process I normally follow on these light-colored horses.


Stock
Horse: [link]
BG: [link]