I wanted to share the process of this composition which imitates a double exposure photography technique.
1. Both your background and portrait layers should be set at Grayscale or a very low saturation to begin with. Feel free to bump the contrast up to help define the images' shadows and highlights.
2. Your portrait layer needs to be above your background with a Blending Mode set to Overlay.
3. Then duplicate this layer and adjust the Blending Mode, but this time to Soft Light.
4. Tweak your Levels in your Adjustment Layers panel to accentuate the contrast between the light and dark areas.
5. The final layer should be a colour wash of your choice – in this case I used one of my studio's brand identity colours – and set this layer to Overlay.