Especially the lighter colors (white and bone) needs more thining. This means that you probably have to apply more than one layer but the result will be much smoother.
For your third edge highlighted mini it looks good. You might even consider doing another highlight with a lighter red on the more exposed areas.
And most of the sharpness of edge highlights come down to brush control and brush.
You might want to look at the tutorials here:
http://fromthewarp.blogspot.de/search/label/line Especially the ones labeled as basics have some advice on brush and brush technique.