Well, first I practiced drawing horses for years. I just recently invested in a Wacom Tablet which means I can draw with a mouse shaped like a pen, this makes coloring much easier. Once I scan in a drawing I use many layers to color following my outlines.
Aw man im jelous, lol. I always wanted to try using one of those pen mouse things.
I just had to use a normal mouse, drew an out line and any other major detail lines/ facial features with the paint brush tool then very slowly built up layers much like you did.
That was my first attempt at doing one on the computer, but I have been drawing for as long as I can remember and painting for a few years now.
But well done, can't wait to see more