A little update. The painting process of the different parts is so slow... I started working on the brake disks. The disks on the top studio set are presented in two parts. The p.e. part was very easy to glue and fitted perfectly.
I also started working on the wood plank on the floor. I sanded it smoothly and masked the plank.
It's done! the painting process was: first layer of white primer, 2 layers of light sand colour, then I airbrushed some layers of different mixtures of flat earth and brown and also some flat black. Once dried, I sanded carefully some wood lines using a rough sandpaper and airbrhused again a light coats of different browns.