On My grill I used Rustolium Rusty Metal primer 2 coats almost wet on wet.Then 2 coats of rustolium High performance enamel 2 coats But i will sand and then 2 mor coats, Now i know its a Rattle can,But the stuff is tough, I used black as well but it does have a slight sheen,there is not much true flat paint out there anymore. i am going to do My bumper the same and My wheels, As for your hub caps You said you stripped them down to Bare metal, They (Rustolium) has a Rattle can for Bare metal...I just do not remember the name,Be carefull when you re-coat..It says re- coat within an Hour..or you have to wait 48 Hours between..Or it will lift on you. I am sure there will be others giving you more ideas,and they will all be good. M/G