I added one more “Colour” mode layer and chose a blue colour to fill the whole canvas. With opacity at 15%, the purpose is to allow the picture to be cooler and the same tone, but you can use “colour balance” to do this as well.
The final result! This is a simple idea about how I work.
Hopefully it will be helpful for you. Any comments/critiques are welcome. If you have any good ideas or suggestions, please feel free to contact me.