On diecast I generally strip the paint with a good quality stripper then file/sand and fix any imperfections in the metal if need be, I then use a self etching primer. I try to let that sit for a week, wet sand, rinse and let it air dry, then it's on to the base coat. I then paint and apply any photo etch trim and I also BMF the trim. After that it gets a good coat of clear. I like to clear coat over the photo etch as it helps keep it in place and less likely to disappear when I polish my models down the road. After that cures for a couple of weeks it gets wet sanded and polished as I did with this one for example. That's my way anyway, I'm sure there are plenty of others.?