hi i have started this project of making this plug 

Hi
I have always used epoxy high build primer,then wet sand and polish but it will not polish to that high of a luster.I have also used Duratec but it still doesn't polish to the place I want to be. Seeing epoxy mould surfaces cannot be polished well I have tried a different technic with my mockup surface because I want a really high luster part. I still use the epoxy primer but then shoot it with black base coat and then 2 part clearcoat.
I wet sand this and then more clear coat. The reason for the black base coat is so I can see if I break through when wet sanding, it is also easier to see what you are doing on the surface when wet sanding.
I then go through to 1200 paper and then #1 #2 #3   3M polishes. The surface is now like a show car and has a very hard surface.
Now I apply my release system and  make my mould.
Hope this helps.
Fred