you can get brushes from DART...they have templates, many many of them,
There other ways as well....
here is a list of speed paints that I follow like the bible when I color
(some are japanese colorist, completely different way of thinking)
http://www.youtube.com/watch?v=1GiJKOESfWo&feature=channel_page
http://www.youtube.com/watch?v=h8Sgg_XH-oY&feature=channel_page
part one
http://www.youtube.com/watch?v=zYc3zJcSt9A&feature=channel_page
part 2
http://www.youtube.com/watch?v=ENNbWDzJfpM&feature=channel_page
http://www.youtube.com/watch?v=A4gidt-YWxY&feature=channel_page
http://www.youtube.com/watch?v=_Cvk9XH2eDY&feature=channel_page
Really nifty tricks and special effects
for me, what I do is fill the shading areas with solid colors> change the hue till I see fit and then erase the edges with a low opacity eraser...makes cell shade with 3D quality if applied to the right places. and then add the highlight, usually purple or blue to the inner sides.
Some people use smudge tool to ease the transition, but it's a dangerous tool and a pitfall to newbies....Though many advanced artists know how to use it moderately.
hope that's close to the question and not off topic
Edit: found another video
http://www.youtube.com/watch?v=ifmKZJrQ3Vs&feature=related