The openings are masked and then a coat of primer is applied

The preshading consists of panels randomly painted in Panzer gray all over the entire surface.

It is then covered with an off white (white with few drops of sky grey xf19)

Even if the original model is even whiter than what I did, I think it is too much white.
So, to mitigate it, I sanded the surface with an abrasive sponge.

After a light gray oil wash, I airbrushed very thin coat of the same light gray to finally arrive slowly to the color that satisfied me.