use hammerite smooth brush on, don't bother paying the extra for specific paint, its not alot different. i've doen mine red, then black and now they're blue. it hought red was too boy racerish, black was too boring and i quite like the blue. matches my coilovers, pulley and now my hoses!!!
take them off before if you can or at least unbolt them so you can clean them up as much as possible and do a proper job.