I created some of my own watercolor brushes by painting different swatches with watercolor and scanning them. Then I imported into Illustrator and used the Color 16 option to trace the swatch, then expanded it. Selected all and then dragged it into the brushes panel. I did the same thing to make a fill pattern by just dropping in the swatches panel.
As you can see the original scanned swatches are not very hard to make and they turned into beautiful brush strokes once converted to vector brushes. I LOVE THE POSSIBILITIES THIS TECHNIQUE CREATES!
This text was filled with the pink-orange-yellow background by using the same swatch I used to create the brush, but instead dropped the vector art into the swatch panel which created it as a fill instead of a stroke! GENIOUS!