The smoother finish was created by using more finely ground pigment in the paint. This style of finish was known as 'Type S' (for 'smooth'). As an example, the colour 'Sky' is usually listed as 'Sky Type S' in a lot of model paint lists and it leads people to believe that it's the official name of the colour, which isn't quite true. The colour name is Sky, the finish roughness (or lack thereof) is denoted by 'Type S'. There were Type S versions of many colours, not just Sky! In the later years of the war smooth finish paints were used on many types for the same reason noted in the Mossie article - increased performance... albeit at the expense of increased visibility due to a glossier airplane.
