Same as you did, just instead of stroking the paths, you fill em..
Start just colouring it to the right colours, then you can slowly begin to add shades, ie. if theres a reflexion, you find out where it starts, and make a path around that fill it with a slightly light colour than the original colour.. then you work you self into the middle of the reflexion and with each shape you make you increas the intensity of the light colour...
like this: http://joaris333.deviantart.com/art/...l-Art-30542108
Just way less detailed ofcourse, just an example so you kinda get the idea,, but 4 or 5 shapes to every colour transition usually does it.. Just beware. it takes shitloads of time doing it right.. But when you finish it, it will look abselutely awesome!