
I’ve used an assortment of watercolor brushes available here at WeGraphics, including the free set linked below.
Free Watercolor Brushes
Insane Watercolor Brush Set
Step 1 – Create the Texture
For the portrait, I’m using
this free image from Stock.Xchng.
Open the image in Photoshop. From here we need to create a very high
contrast version of the image. To do that we first need to desaturate
the image (Cmd+Shift+U) or (Image | Adjust | Desaturate). The we need to
punch up the contrast using levels (Image | Adjust | Levels).

To create the texture, I used a custom brush of solid text. You can use any font that you like, but I chose
Mutlu for its ornamental loops and curls.
Create a new blank document 700×700 pixels and fill the document with a block of black text.

Now click (Edit | Define Brush Preset) to create the custom brush.
Back to your portrait image, create a layer mask for the girl’s layer.

Fill the layer mask with solid black, which will make the girl
disappear. Using your newly created custom brush, select solid white for
your foreground color and begin to click on the mask to reveal portions
of the girl’s face. Experiment with different opacity settings for your
brush.
Step 2 – Add the Watercolor
Now on a new layer above the portrait, begin adding watercolor with
single clicks, using a black brush. There’s no specific method here.
Just do what you feel looks right. Don’t go overboard, less is more with
these splatters. You don’t want them to detract from the subjects face.
Step 3 – Add a Little Color
To add color, we need to create a Gradient Fill Adjustment Layer, and
set it’s blending mode to Overlay. You can use any colors you prefer.
Below is the gradient that I used from the default selections.

As I mentioned before, this effect seems to work with just about any photo. Below is another example.

I hope you found this technique easy to apply, and I hope it also inspires some experimentation!