Yep if you plan putting a bandaid on it, cleaning surface and bondo works well. But ultimately plan on either replacing the panel( or in your case door). I was forced to bondo some rust on my truck when i got it because it had to be my DD, and it was beginning of winter. That was 2 years ago and some rust has started to pop through the primer that was applied on top. I knew it was going to happen, honestly i thought it would be sooner. So now time to get to work and cut the rust out:madgrin: