Paintwork

First I used putty to fix the imperfections, and then I sanded the entire cabinet:

Then I applied a layer of primer (MDF is quite absorbent):

And finally the cabinet is painted with black spray polyurethane paint:

Paintwork finished:

With the back covers placed:

By the way, we must recognize that the living room is not the best place for sanding and painting. But when you have no other place...