I use that stuff alot at school. Works great on bare metal spost or like you said on rust repair. Only down side is that stuff sands like crap, use a mud hog sander on it to get it level. That will save alot of time. Ohh, make sure you use the correct hardener (liquid) and plenty of it. good luck
I agree the best way is to weld in new metal. But this is way better than just standard plastic filler, it has better corrosion resistance. I'll be fixing my doors soon, I plan on grinding down the rust bubbles, using this stuff and self etching primer and epoxy primer, should last plenty long.
Yes, I agree throwing in new metal, but where the repair is needed, its tough to get new metal in there. The repair is right above both front windows and on the drivers side windshield pillar. So far the repair looks really good.