Adding Textures in Post Production
For this example of adding texture in post production, I started with a portrait.
I then took a picture of a tree as texture. I got the texture from textures.com.
I copied this texture in post onto the portrait. Then lowered the opacity to about 60% I then used a blend mode on the texture, making it screen. From there, I used a mask to take the texture off the subject in the portrait.