I have stripped down some body parts to bare metal and coated them with the rust converter enamel. No when I go to address the little dings and imperfections in the panels should I strip it back to bare metal or just rough up the surface of the rust convertor before applying the body filler?
I have always taken panels down to bare metal before, but I don't want to lose the protection from the rust convertor nor do I want to have chips of bondo fall off the car at a later after it is painted.
Bondo should adhere to the rust converter. I've done it in the past with no issues.
It will be hard to get a straight answer on the Metal-Filler-Primer or Metal-Primer-Filler question. The filler makers want to go on first, the primer makers want to go on first.
That said, the majority of people go with Metal-Filler. You should get a better grip on roughed up metal then roughed up paint. Rust cannot start if there is no moisture and oxygen so either will stop rust if they are properly put on. In either case there can be no holes to the back side (filler will absorb moisture eventually)
The real question here is, if you have stripped down to metal and cleaned up the metal, why do you need rust converting paint? If there is rust left on the metal and you paint over it, then go with the filler over the paint.
The best way to do it (from what I have seen) is to go down to metal, clean / remove all rust, put metal prep (acid) on metal, add filler, paint with best primer you can (epoxy), then paint.
BTW - I am assuming you are using Bondo as a generic term. If not, do yourself a favor and don't use Bondo. I don't think Bondo as a filler is inherently horrible, but better quality filler is MUCH easier to use and will likely be much more resistant to bending.
