I've been digitally painting using my Wacom tablet and various iterations of Photoshop for about 9 years and over that time I've tried various settings for brushes, opacity and fill and tried nearly all of the endless options Photoshop gives you. Recently I've been paring back the amount of different options I tweak while I digitally paint. I'd typically change brushes countless times and work on different elements on separate layers. I've now started to paint exclusively with one brush and on one layer.
For those interested, I'm keeping my flow at 30% and opacity at 70%, probably the biggest change to how I've painted in the past - normally I'm constantly raising and lowering the opacity while working. Now I'm changing the colour I'm painting with as I'm going using the eyedropper tool (holding Alt with the brush tool in use gives you quick access).
Here are some screen grabs I took while working on the recent Scott Pilgrim poster. By no means a tutorial, it show the work at various stages.