I have been doing body work all wrong.

OK. It is confession time. I used to Patch rust holes without welding, but there is a decent way to do it. I used to patch smaller holes (2" or less) by cutting all rust out, grinding about 2" past the edge of the hole, tapping the edge of the hole down, and making a patch with several layers of fiberglass mat and JB Weld epoxy. I tried to wind up with a surface that was almost level with the surrounding area. Then I would do filler work. For larger holes, I would cut all rust out, grind about 2" past the edge of the hole, tap the edge of the hole down, and make a patch with sheet metal. Then I would drill holes through the patch and car area, smear the area with JB Weld and pop rivet the patch into place. Then filler and primer. Now that I am pretty good with welding, that seems like a hack, but it lasted 20 years on one car.