Get a small wire bottle brush and do the best you can at brushing the inside of the door to get rid of any loose stuff. Then use a craves tool on your shop vac and suck out all the dust and dirt. Then take painters tape and tape the drain holes closed on the bottom of the doors. Then pour in about 1-cup of POR-15 through the door access hole. Then use a throw-away 2" foam paint brush taped to a paint stir stick and start dabbing/brushing all the surfaces you can get to. The top edge of the brush will get under the horizontal brace.. Make sure you coat the entire bottom seam. Add more POR-15 if needed.
When done and before it dries pull the tape off the drain holes and let the excess drip out over night...
I always re-check the doors anout 2-hours later to make sure the drain holes are still open, as the POR-15 starts to dry it gets thicker and could stop up the opening. It's easy to clear the holes while it's semi soft.
That's about as good as you're going to get it and should last your lifetime.
Don't forget to wear gloves as any POR-15 you get on your skin will be there for weeks!
Mike B
