Thank you, everybody.
FF, the surface detail is indeed emphasized with wash.
A progress? Well, I have completed staining the airframe around the engine and on the underside. I have also attached the cabane struts. They have some tolerance at their sockets, so to keep the geometry right, I have used the top wing put on them and aligned with respect to the lower one. Today I plan to add the interplane struts - some photos will follow then.