Well, I somewhat like the flat because you can see the skin/paint details easier. With the shinny, I get the impression that they put a coat of wax over some badly oxidized paint. If they were keeping the bird polished up, the paint wouldn't get in such bad shape. In order to get the shinny to work, the green would need to be darkened to keep the contrast with the white of the horse for example, and there would be fewer stains and faded/oxidation patches. The color temperature of the specular values would also need to be raised so the reflected light is not so yellow – it is killing the blues. But doing things like that would take a lot of work and would change the personality of the skin, which gets into the Artist's interpretation of the paint scheme.
I don't mind a little shininess (except for the yellowing) but just simply adding some specularity did not give the skin a polished-look like I hoped. Thanks for trying it.
