first you have to find out if those grey bars are raw plastic or if they've been coated with a vn bumper coat colour over the top. if vn bumper coated all you need to do is rough it up with some red grade scotch brite, wipe with wax and grease remover and paint right over the top. if raw plastic same process you just need a medium wet coat of plastic primer before top coat paint... to fine out what its already coated with (or not coated) find a spot on the bottom of the bar and rub it with some sand paper (say 4 -600) see if you get dust on paper or just little bits of plastic sort of rolling off the paper....
dont sweat the petty... pet the sweaty...