A photoshop watercolor paint tutorial to using a paint image and portrait. here what i did is make a group then drag the paint image to group the hide this group for a while. select portrait layer go to selction then color range apply this color range and get a selection. make sure the group and press mask icon and invert this mask by pressing CTRL+I. make a new empty layer under the group, fill it with white. now you get watercolor painting effect easily.
link for water color