I have put in several headliners and I would make a couple of recommendations to you. First, somehow mark the bows so they don't get out of sequence, then sand the rust off each rod and wax the metal LIGHTLY (you don't want a glob melting through in the hot sun). When you get the rods inserted into the sleeves and the rods inserted into the roof brackets, you will want to be able to slide the headliner slightly side to side to remove wrinkles and puckers. The 'slick' rods make this a lot easier.
my $ .02