I sprayed some gloss black paint out into a small tub and then brushed the paint onto the wheel trim sections with a thin, soft artist's brush. You can effectively wash the paint on and get it into the corners very neatly. The beauty is that the spray paint likes to gath together and find its own level so it dries very evenly.
You might need two coats, but it's a very durable finish. I know coachbuilders used to use this technique on cars in the very early days of motoring to get a glass-flat, high-gloss finish with a deep shine on the bodywork. Works very well for the small bits on the trims anyway! The paint just needs to be thin and 'wet' - ie, just out of the can.
Michael