I just ordered and am waiting for rust eliminator. I have a small amount of rust coming up at the seam under my doors. You know, where the lip of the bottom of the door goes under and back up on the inside. How should I apply the product to best solve this problem? Should I open the door panel and try to brush this product into the area at the bottom of the door where the water goes? I was thinking of using a paint brush to scrub the dirt from this area inside the door and wash it out and dry it. Then paint the product into the seam down in the bottom of the door. If that works, should I caulk it or something?