Scary indeed, I get out of it as often as I can, which gives new meaning to "out of my mind."
The work flow on developing new brushes is really simple. I am constantly watching traditional artist work, buying their books, and looking at their paintings. I haven't painted traditionally in over 40 years, but a week or so ago, I got really crazy and ordered a bunch of watercolor supplies. I still had my butcher pan watercolor palette circa 1965. In the last two days, I've played a bit with the traditional stuff. I am quite surprised how different it feels from what I remember.
Yesterday, I watched a tutorial from Linda Kemp. Normally, I would try to do what she was doing, but in Painter. This time I first tried it using traditional paint. It was fun, but not too successful; it is going to take a lot of practice on my part. Anyway, Linda loves the granulation that occurs with watercolor, and I was noticing the granulation in my practice piece. I checked a few of my custom brushes in Painter and started playing with granulation. Linda uses watercolor very thickly. Where thick it is very dark, but she pulls the color out to a lighter value. So, I took some of the granulation brushes and brought up the opacity, concentration, and viscosity. Now, I was getting something akin to what Linda was demonstrating. She was also using a 3/4" flat, so I squeezed the variant and set it for rotation.
That's really all there is to it. I watch traditional watercolor artist and try to mimic what they do.