For the past three still lives I've used pretty much completely different methods of starting. First one was an amalgamation of brushes, just getting warmed up. Next, I tried to block everything in with a hard brush and exact colours. Now I tried blocking in with a soft round airbrush and approximate everything, then refine colours, edges, values and drawing as you go along. I think this is the method that saves you the most time in the end. You can leave most of your painting with soft edges and "averaged" colour, but then tighten up the areas of focus, and find a way to guide the eye creatively. The danger here is it's very easy to make the entire painting swim in mud.
I've also been thinking a lot about colour transitions, and trying to make them as efficiently as possible. Highlights, for example, take at least two tones (usually a saturated soft one first, then a dull, bright, hard stroke on top) to pull off. I think ideally you want to simplify the picture down to as few colours as possible, and still retain all the information in the picture. That's where the "skill" comes in.