It can be done with butt welded (TIG, or Gas welded I guess), properly finishing the welds, hammer/slapper on dolly, shrinking disc, etc.

I hear it a lot, "you should never use filler." I agree, it's not ideal, but when you use high quality products and do what I said above to a level of 90%+ perfection, it's really the only realistic way to do a car. You could also lay down some spray-able polyester and say "no bondo," but it's the same thing and when sprayed all over the car and in the jams, it looks puffy and just a little off.

I hear metal guys say, I don't need filler, but I'm thinking when he's not looking and the body guy/painter is using a 3 foot block with a guide coat and imperfections are showing up, it's just kind of the way it is in my opinion.

Lead is great, I have used it, but, toxic, cancer, right?

I usually recommend new panels/steel, when things are ugly, but sometimes fabricating patches are the way to go, all a judgement call. A new quarter panel is beautiful thing when doing a complete rotten to the core, collision damaged 911.

What are your thoughts? What products/techniques are people aware of, do themselves or like?