Pull (peel) a few feet of the gasket out of the metal channel and let it hang. After scraping, brushing, sanding, cleaning, and painting the channel, let the paint dry and then re-install the gasket in the channel. (That takes a bit of poking with a small screwdriver.) I'd let it dry 6 hours unless you plan a second coat -- then let it dry 1-2 hours first.

Be careful of using POR-15. POR-15 is an incredibly hard, durable coating that adheres to and seals a metal surface unlike any ordinary paint.

But if you have any rust left on the metal, POR-15 will adhere to IT, not the metal, and will eventually fall off. POR-15 does nothing to stop rust other than seal the metal surface from moisture. Any remaining rust between the metal and the POR-15 can leave a pathway for additional moisture to enter, which means more rust -- I've seen it happen.

Corroless (or whatever its new name) chemically converts the rust from iron oxide to iron phosphate. Corroless is chemical protection; POR-15 is mechanical protection.

POR-15 is unparalleled for sealing a surface that's exposed to abuse, such as a floorboard or inner fender or undercarriage. Corroless is good for stopping rust in protected areas, such as under gaskets or under carpets or inside rockers. POR-15 is hard as nails, Corroless remains somewhat soft and can be abraded away -- so should be used only in the right places.

--
Don Foster (near Cape Cod, MA)