How to make it appear as paint is dripping over photo of brick wall?

Try adding a Bevel & Emboss layer style to give the drips some depth

This used the Texas Chainsaw Massacre plugin 😉

Hi The effect that you want can be achieve pretty easily using the Blend modes

To get the paint lines, use an irregular shaped brush like this

Here are the paint lines with out any blending:

Here is the lines with the Layer Blending mode set to Color Dodge: There is not a lot of difference except where the the mortar is which gives you some delination and you do get some intereaction with the background

This option uses Soft Light and multiple layers 

I used the same image of the paint stripes set to Soft Light and duplicated for three layers. And the beauty of this is you can do as many layers as you want to achieve the effect. If you want it stronger, and another layer.

Let us know if you have any quesitons?

Michelle