So, this is probably a dumb question, but I can't seem to find a clear answer.

I'm shaving my engine bay. I have welded up holes and shaved the studs in the firewall. I'm at the point where I am adding filler. I'm using Rage Extreme for filler. I've also got some spots down to bare metal. Should I be coating the metal with etch primer then applying the filler on top of that or is it OK to apply the filler directly to the bare metal/scuffed surface?

What's the preferred method in my case?

 

its ok to put filler on bare metal as long as its a scuffed surface

 

I've done that. I'v actually tried to chip away at filler on the bare metal. It has a good bite on the metal and is not easy to get off.

I was a bit nervous there for a min.

Thanks