here's how i create a watercolor text effect in photoshop. 

1. add a text on your canvas. mas maganda kung script or handwritten typeface. i used king basil lite on this one. you can start off with any color because that wont be necessary. 

it should look like this: 

2.  located on the layers window, ibaba niyo yung fill opacity to 0%. the text should be invisible. tapos, ctrl+click niyo yung thumbnail nung text layer (yung naka-encircle sa picture). then make a new layer. make sure na nasa new layer na tayo ngayon.

it should look like this:

3. choose a color that you want and add your brushes. dapat mas malaki yung size ng brush mo kesa sa text. if you're satisfied with your result: press ctrl+D to deselect.

it should look like this:

tip: dapat sa isang place lang kayo magaapply ng watercolor brush, kasi kapag kinalat niyo yung paglagay, pangit tignan :)

my result:

i'll leave the watercolor brush that i have in the comment box. hope this helps! :)