Once the drip rails have bends in them it's pretty impossible to get them really smooth looking again. Taking them off incrementally, as mentioned in chakra's post, may be possible but I never had any luck with it. In my opinion, buying them new and unbent (Volvo sells them for a little over $100 I believe) would be best. Center the rail onto where it should be placed, and as long as your paint/repair job didn't alter the diameter of the rail's body significantly, they should snap on fairly easily with some pressure from your hands. Like the bendy and fragile windshield aluminum trim, I think it's much easier if you have another pair of hands to hold the trim in place, to stabilize it and so prevent bends.

good luck,

Holly