Take your time on each of your miniatures, but break the time up into phases of painting. Start with your basic 3 color scheme for all the minis you'll field, then work your way around to additional hues of each color, detail your favorite characters, spend time on making them your favorite miniatures. You want to get your force playable, then beautiful. But don't rush to the final phase of painting for a tournament or a skirmish, they're'll always be another scrap and a chance to dazzle your opponents with your finished paint scheme later, but you can't strip away a rushed paint job as easily.