Have you ever tried cell-shading? I guess I should start off by saying do you use a tablet? Because it just makes coloring in general so much easier.

I have a Bamboo Fun tablet. It works okay, but I still find it hard to decide which colors to shade with - I always end up in this state where, things either look TOO heavily shaded to the point where they're overly "shiny", or else not shaded enough x.x

I have done cel-shading before, but not in a lo-o-ong time. I think the last time I attempted it was this picture:
http://www.furaffinity.net/full/2908553/
Like 2 years ago! It's probably not a bad idea to give that a shot again.

Your cell-shading appears to make more definition in clothing, which is why I like the style so much, because you can have simple line work (like my own) and I like seeing it come together - the hair and folds - with cell-shading. Also, maybe shade with just one shade of a color? I used to try to match the shade of a color to each base color but found it easier just to use a shade of grey to do everything. Maybe try it for kicks? :]