This video describes how I repaired two large holes in the rear wheel wells of my 99 Subaru Forester. There is also a small part of the video that shows where the filler neck often rusts out and what I did to repair it.
Tools used: various sheet metal sheers, flat screwdriver (for scraping), air powered dremel tool with a wire brush attachment, impact driver, selfdrilling sheet metal screws, wheel wrench, car jack, etc.
Materials used:
12x18" piece of sheet metal, some rubberized rock guard, autobody seam sealer, tremclad primer spraypaint.
This took about 34 hrs per side to clean, prepare, install and coat the inner wheel well. It's a messy, dirty job but my car body should last a few more years because of it. Next step is to get it sprayed with 'rust check'.