I haven't done any pealescent effect myself, but I have tried to create metallic colours, by mixing metallic paints (silver) with the colour of choice. But this resulted in a dulling down of the colour, even though the metallic effect did work as expected. I experienced this effect in both acrylic and enamel based paints.
So a bright red and silver became a dark red metallic...
I do know that there are several products on the market that can be used as a wash over an existing colour, and I'm fairly certain that a pearlescent effect is among the offerings.
Alternatively, you could (since it's a metal mini) think about getting white pearlescent nailpolish and use that. Don't use it on plastics though, as it'll probably melt the mini
