I painted my callipers over 2 years ago now....and never used a primer at all...Whoops, didn't even take them off the car LOL
I did clean them up first though

....with a wire brush and Meths to clean thoroughly etc...
Good luck with it...take your time...make sure you leave them to dry between coats
I did both in the same day and had my mum drive me to work in her car the following day
....just to make sure it had cured long enough
they still look fantastic 2 years later IMO...although when my dad decided to clean my wheels (which i hate him doing anyway) he used an "alloy wheel cleaning brush" which has plastic bristles...on a metal wire...so he chipped the paint going between the spokes <_<
... you can hardly tell though...so it's not all bad ^_^
Annoyingly (although it looks nice and sunny in the picture) it rained that evening so i had to balance a pair of rubber car mats over them to keep 'em dry

if you have a garage door or carport to go under that would be easier
never even thought to laquer them...maybe i should do over?...