Color! How did you go about the coloring of it? :3

I posted this in order to illustrate the short explanation I gave you in the final picture.
To give you more precision I created a color layer (mode multiply) for the flat colors.
Then I duplicated the visible layer into two new ones: darken one and lighten one.
I respectively used them to add shadows and highlights, like in this picture : http://fav.me/d5ir76v
I hope it somehow answered your question.

Nice! I'll have to attempt to try this method!

ohh, but the colored you make in the compture? :)

Exactly !
It is much more easier to color it on the computer.
I also added some sharpness on the dip pen.

Very nice indeed. I feel rather envious, I never have luck when using a pen to draw things.

Thank you very much !
If you have the occasion and the time, you could perhaps try to ink your drawing with different types of dip-pens or markers and try to find which ones suites you more.
Failing at a traditional inking (especially when it took you days to do it) is very annoying, but it happens. I often felt it in advance if something would be wrong or not during this step... but I never listened to my feelings and I often repeated the same mistakes.

He is so cute, makes you want to hug him and pamper his cute paws