I use Dullcote to bring the various lusters of paint into line with each other. As you might guess by its name, Dullcote’s sheen is flat, not at all shiny. So I will follow with a LIGHT coat of Testor’s Gloss. This give the final effect of a slight shine, not unlike manufactured plastic, thus helping the illusion. But don’t go too heavy with the gloss, as too much tends to remain tacky when used on plastic.