I've been playing a lot with both watercolor and "real media" digital brushes lately, so these types of effects are on my mind. Thanks to Bonnie Christine for pointing out the class and sharing an inspirational project!
To try the watercolor effect, I used a digital inking brush with a smooth texture and slightly rough edge to write the text and sketch a simple flower. I put them on separate layers so I could adjust the styles independently. I ended up using "coal" for both, but set the blend mode to normal for the text and vivid light for the flower. It's very fun to see the way the effect changes with different blending modes!
I enjoyed trying this--it's a great tool to have for designers who switch back and forth between digital and traditional media.