How to make whole object transparent in rendered result

I have an object of a tree and a car in my scene that take to much attention so I want to make them more transparent so you’ll be able to tell they are there but that they are not the main thing to look at.
How can I achieve this goal?

In the tree object I have two materials, so I can mix shaders with the transparency shader but the result is not so good in term of looks. Also that wouldnt work with the car beacuse it has dozens of materials and its not a good solution to go and change each individually + It might not look good as with the trees.

Thanks for the help

Image reference for shading ant result: (this method isn’t applicable to the car object because it has lots of materials)

EEVEE seems to be not good at transparency, use cycles.

I am using cycles…

Oh, sorry i was too quick while reading and thinking "what’s the [email protected] and just checked your settings and they are okay. But now i see your trees are transparent. So maybe you just want to render your objects and make them transparent in post production ?

To render them separately or in different renderlayers might be a good idea anyway, otherwise overlapping planse become visible. (like at the branch forks in your image.)