Well
i removed all the brass with an home made tool ( i've curved a very thin file just on the point), and removed carrefully the brass . Think there is no more inside but i really can't be sure , the hole is too small and too far.
I will order a new screw and will see i can put the new one, it should be OK unless there is brass staying inside or unless i've killed the airbrush body threading
Whatever, don't be as stupid than me, when you clean the full airbrush or change the needle ring : be soft with the tightening and be sure to use the right size screwdriver to remove it
Pat