Brush the damaged area to remove rust powder from the remaining metal. Treat the damaged area with rust inhibitor. If the back of the damaged area is accessible, treat it as well.
Before applying the filler, you need to seal the hole. This can be done with zinc mesh, aluminum tape or polyurethane foam.
Zinc mesh is the best material for patching large v holes. Cut a piece to the appropriate size, then place it in the hole so that the edges are on top of the surrounding body metal. The mesh can be secured in place with a few lumps of filler placed around the perimeter.
Aluminum tape can be used for small or very narrow openings. Unroll a piece of the required size from the roll and stick it over the opening, placing a second piece covering the first if the width is not enough. Press the edges of the tape with a screwdriver handle so that it fits well to the metal base.
Polyurethane tape is good for holes located in areas of the body with a complex configuration. The foam preparation procedure is as follows: mix equal amounts of liquid from individual cans included in the kit in one container. Wait until the mass begins to thicken and pour it onto the hole, placing a piece of cardboard underneath. When the polyurethane begins to expand, it will protrude from all uncovered holes. After it has completely hardened, cut off the excess with a hacksaw blade.
ATTENTION: In case of major damage to the body, it is necessary to carry out a major overhaul, during which the damaged sections of the body are replaced.