I don't have Photoshop, so I used Affinity Photo for this project. The process of creating a brush is different, but the results are similar.
I created an Image Brush from a watercolour texture swatch and used the brush to create a background for text. I experimented with blending modes for the layers as well as an outer glow effect for the text to achieve this result:
Click on the picture to enlarge it and see the details of the text.
I did Helen Bradley's Photoshop Brush Tips class at the same time as this one. You can see my project there at this link: https://www.skillshare.com/classes/design/Photoshop-for-Lunch-10-in-10-10-Brush-Tips-in-10-Minutes-or-Less/893709734/projects/83437?via=class-details-projects-page